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Color In Medical Products

By Dan Stipe, Forma Medical Device Design

The delivery of health care is evolving to take into account the entire patient experience. Medical products and devices have a significant impact on that experience. Their colors can be calming and restorative, or they can be active and energizing. Further, many medical products that were once used exclusively in controlled care settings are now being used in the home. In the home environment, medical products require aesthetics more in line with consumer products. In appealing to consumers, color has great importance.

Why Color is Important in Medical Products

Color is one of the most important things in our lives. Colors affect us emotionally and psychologically, often to a degree that we are not even aware of. Color is no less important in medical product design than it is in other areas.

A Technical Note on Color

There are many different models for describing and specifying color. This article was written mostly from the perspective of the Hue-Saturation-Value model (HSV).

When most people think of or talk about a “color”, what they’re usually referring to is its hue – red, green, blue, yellow, etc. Hue is just one dimension of a color, however. Colors also have different levels of saturation and different levels of value. Saturation is a measure of how “pure” a hue is, value is a measure of how light or dark a hue appears. More on these below.

What Color Can Do

In addition to its emotional and psychological effects, our perception of color can be used in a functional manner to help us organize, group and understand.

In the hierarchy of our visual system, the first thing that attracts the eye (after movement) is contrast – first contrast in value (dark against light), then contrast in hue. By highlighting with color the areas of the device that the user needs to interface with, you can provide the user with a cognitive map of how to quickly “read” the device so they intuitively know how to turn it on, where to push, pull or lift to open an access port, where a luer gets attached, or simply, what are the most important controls to interface with:

In addition to attracting our attention, color is also very powerful in providing a system of organization. You can use color to divide a form and define different areas of function and importance. This is a technique that can be used in a very subtle way yet still be effective, for instance by using different shades of gray or different values of the same color. You can also use color to group items or functionality:

Another characteristic of visual perception is that we perceive light-colored objects to weigh less than dark-colored objects. You can employ this characteristic to make a heavy object seem lighter, or to suggest that an instrument has a base that is sturdy and well-anchored. You can also use the value component of color combinations to make a device appear smaller: use a light color around the periphery, a darker color at the interior:

Objects high in their value component (that is, light-colored objects) also encourage that they be kept clean – it’s easy to see when they’re dirty! That’s one reason why light colors and pastels predominate in medical devices. This is beginning to change though, as some companies are using bolder, more saturated colors in an attempt to distinguish their brand. Medical product companies need to be careful in this regard. Bold, unexpected colors can be appropriate is some cases, detrimental in others.

The bottom line is that color can be used to increase the functionality of a device by making it easier and more intuitive to use.

Why Choosing Colors is Hard

Choosing color is a moving target. Response to color varies between successive time periods (trends/fashion) and between cultures. Colors and color combinations also take on connotations due to the way they are used commercially (branding) and how prevalent they become in that context. Colors and color palettes also cycle in popularity. Indeed there is an entire industry based around predicting color trends. Medical products are less prone to being influenced by fashion and trends, but color popularity does have an impact on color choice for medical products: using popular colors makes products seem current and up-to-date, as opposed to seeming dated. The psychological effect of using the “latest and greatest” should not be underestimated.

So, how can a developer of medical products bring some reason and rationality to an endeavor that will remain subjective?

Understand the User

When considering color, you need to understand who it is that will be using the product and what will appeal to them from a color standpoint. “Appeal” doesn’t mean what colors do they like. It means what are the characteristics and values the user will associate the product with. Does your (typical) user want the product to feel precise? Intelligent? Durable? Sophisticated? Etc. Are there particular colors/color combinations that they associate with those characteristics?

You can obtain knowledge of the user via a number of methods. A discussion of those methods is beyond the scope of this article. The point is that if you don’t know your user, you won’t be able to select product colors that will help the product sell and be well received in its market.

Understand the Goals

Once you understand your user, you can begin to devise a design strategy for developing a successful product – one that appeals to users and satisfies their wants/needs. Beyond the medical function of the product, what are you trying to achieve with your design? Is your primary purpose to make the product easy to use? To make it appeal to a particular market segment? To give it an aura of precision, strength, etc.? To make it feel calming – or exciting – or fun? A good strategy will combine a number of elements that, when brought together, will achieve your goal. Color is one of the most powerful of those elements.

Understand the Context

Medical products should be designed form an understanding of the context in which the product will be used. Context includes everything from the physical environment surrounding the product in use/storage/transport to the ethnic culture(s) in which it will be used. To understand context – and choose appropriate colors for that context – you should look at things such as:

Existing (competing) products: What are others in the product space doing? Are their colors bold? Subdued? Should your product be consistent with the competition, or should it be markedly different? Are there certain colors that are expected?
The environment in which your product will be used: Are there particular colors that dominate the environment? Is the environment visually busy, calm or in between? Will the product be used primarily in a hospital/clinic environment, in the home, or in public? How do you want your product to sit in that environment – should it stand out or should it blend in? Does it need to be discreet, or could it be a status symbol? Will the product be used in a resource-deprived setting? Are there any color implications to that?
Cultural considerations: Do you know what various colors symbolize in different cultures? How strong are those symbolic associations? Can they be ignored in favor of using color that will promote other design goals?
Corporate colors: Many companies are tempted to use their corporate brand colors in their products. That can be appropriate if the brand colors fit with what the product needs to accomplish. Unless that is the case, the temptation to use corporate colors in the product’s color scheme should be avoided.
Sterilization method: If your product is reusable, you need to consider how the sterilization method will affect the color of the product. EtO and gas plasma sterilization does not have a significant effect on color. Radiation sterilization using gamma or e-beam will cause a color shift toward yellow. Color-shift will be most noticeable in transparent materials.

A Methodology for Choosing Medical Product Colors

Choosing color does take some experience and aesthetic sensitivity. There is no system you can apply that will ensure that you pick the “right” colors every time. There is also plenty of room for artistic latitude. Yet, there are characteristics of color and our response to it that we can use as guides to make thoughtful, considered decisions about how we use color in the design of medical products.

Color Temperature

Start by choosing temperature. Most products will have one color that covers most of its surfaces. Should that dominant color be warm, cool or neutral? Look at a typical color wheel:

The green-cyan-blue side is cool, while the yellow-red-magenta side is warm. Most medical products currently and historically have used greens, blues and colors in the neutral space of whites/greys. There are several reasons for that. Most importantly, the cool colors – blues and greens – are calming colors, which is what you want in the anxious environments of hospitals and clinics.

David Pantalony authored an interesting article in the Canadian Medical Association Journal⁽¹⁾regarding how green became the color of hospitals and medical machines. He cites an American surgeon, Dr. Harry Sherman, as being the first to use green in the operating room in 1914. Finding the traditionally white environment to be too bright and glaring with new electric lighting systems, Sherman experimented with an operating room all in green, reasoning it was the color compliment to the red of hemoglobin. He found that his eyes could rest on anatomical features and details much better and without tiring. Around the same time, using color as a therapeutic treatment came into vogue, with green used for its calming qualities. Eventually, use of green in hospitals became pervasive.

Warm colors are great for accent colors, and for color coding purposes and for attracting attention. The contrast of color against a neutral background is easily perceived.

Although warm colors will be used mostly for accent and effect, there are times when you might want to consider colors from the warm side of the wheel to be the dominant product color.

Warm colors are basically energetic and happy. You might want to use warm colors for products designed for use in pediatric care. Another area would be obstetrics/gynecology – associating pink as being feminine has a very strong bias in our culture. Purple also has a feminine association, though not as strong as pink. Similarly, medical products designed for ailments exclusive to the female anatomy could use warm colors as their dominant.

Finally, warm colors, if not too vibrant, will promote a feeling of physical comfort – food, warmth and shelter (home). This suggests that warm colors could be considered for products used in recovery and patient rooms. Be aware of the contradiction here though: warm colors are comforting but cool colors are calming and restorative. Which way to go will depend on what you’ve learned about the user/patient.

Neutral Colors

By and large, the best choice for the bulk of a large medical product’s form is going to be one that serves as background onto which color and value contrasts can be selectively applied. White and light gray are good starting points. Pure white signifies cleanliness and purity – perfect for a medical product – but too much white can be overwhelming. When designing products for use in the operating suite and other environments having areas of high illumination, be sensitive to the fact that white reflects the most light, causing glare and tiring the eyes. Giving the product’s white surfaces a matte finish will mitigate those problems somewhat.

Limiting your palette to white and light gray is just that – limiting. Subtle additions of hue can provide a significant shift in how the color feels, while still keeping the surfaces predominantly neutral:

A functional reason for employing white, light gray or subtle tints is because unclean areas will contrast against the light background, making it easier to see whether the product has been cleaned thoroughly.

A reason for employing darker colors would be if the product is reusable and will be sterilized using gamma or e-beam radiation. Those methods shift colors toward yellow (to a varying extent, depending on the material). Any yellow shift will be less noticeable in dark colors.

Which Neutrals?

In the ultrasound cart at left, the use of dark gray implies serious, no-nonsense. “I’m here to do a job”. The dark gray also provides a contrast to the light gray, thereby drawing your attention (a cue that makes for good usability) to the handle (which also attracts attention because it’s the only form that’s set at an angle). Dark gray is also used at the control surface – the area of the machine that will be touched the most and therefore will have a tendency to get dirty. The dark (low) value of the grey will hide smudges.

Light gray is the dominant color. It also says, “don’t pay attention to me – I’m in the background”. The relatively high value of that gray makes the cart feel visually lighter. If the gray were darker, such a large machine would feel ponderous. If the dominant color was white instead of gray, the cart would also take on a different character. It would feel “purer” (which isn’t necessarily needed in this context), “happier” and would attract more attention to itself, detracting from its seriousness. The monochromatic appearance furthers the effect of solid, business-like seriousness. The few areas of pastel accent color add an element that mitigates the austerity of gray and helps make the machine feel approachable and not intimidating.

Neutral Value Synopsis

White: pure, sterile, bright and happier than any tint of gray.

High value gray: more serious than white but still possessing lightness. Will call less attention to itself than white will. Provides a good background field against which to apply contrast.

Medium and low value gray: As you move from high value to low value, the colors get heavier. One application of the darker grays is to use them at the base of an instrument to suggest solidity. Use medium or dark gray depending on the impression of heaviness/solidity that you want.

Neutrals other than Gray

Browns and its tints (beige) can also be considered neutral colors. Browns are to be avoided because they associate with dirt and decay – not good for medical products. Beige and other light tints of brown could provide a warm neutral color. Products that you want to blend into a person’s skin color (a hearing aid or electronic patch, for example) could use beige. Beige has also been a popular color for medical carts and large units such as ultrasound systems. Beige is much less popular currently, I believe because light grays have a stronger association with high-tech, which many companies want to promote in their products.

For medical product design, a good way to achieve a warm neutral is to add a small amount of yellow to a high value gray:

Color Value

The warm/cool/neutral decision will most likely be relatively easy to make. The next step in narrowing your color choices should focus on the value dimension of color at areas on the product where the user will need to interface.

The terms “value” and “brightness” are often interchanged. Value refers to how light or dark a color is:

Differences in value creates contrast, and contrast is what our visual system perceives the quickest. Contrast is also created by a color hue against a neutral background, but in most cases it’s created by dark against a light background or light against a dark background. Because our eyes perceive contrast first, designers can use it to direct the user’s attention to the most important areas of the product.

It’s important to keep the contrast effect in mind when choosing which hues to employ in the product because different hues can be similar in value. Here is an interesting illustration from Bruce MacEvoy’s Handprint.com of the importance of value differences:

This is Edward Hopper’s “Lighthouse at Two Lights”:

When you remove hue but keep contrast, the image is still easily recognizable:

However, if you keep hue but remove the value information, the image is much more difficult to interpret:

A technique that artists use to judge value differences in a painting is to squint their eyes. That makes value differences stand out. Per MacEvoy, the most accurate way to judge value difference is to view the object in very dim light, when only the eye’s rod receptors (which can’t sense color) are active.

Color Saturation

Saturation refers to how dominant a hue is in comparison to grey:

The difference between saturation and value can be confusing. A hue becomes less saturated as it moves higher in value (by adding white to the hue – a tint). But it also becomes less saturated as it moves lower in value (by adding black to the hue – a shade). A good way to think about saturation is to consider how pale or how strong the hue is. ⁽²⁾

As it relates to medical product development, you can make decisions regarding saturation levels by considering whether you want a bold effect or a soft effect. Highly saturated hues will be bold. Less saturated hues will be soft. Bold, saturated colors can be fun and uplifting. As such, they can be appropriate for therapeutic products and for devices to be used in pediatric settings. Soft, tinted colors, regardless of hue, are more subtle and calming:

Other Color Choice Considerations

Surface Finish

The finish of the surface can dramatically affect the way the color is perceived. You can make effective use of a single color by treating some components with a matte finish and others with a gloss finish:

You can also use three or four different texture levels to create a value composition using a single hue. The difference in the way light is reflected from the different surfaces will create a variance in value levels that the eye will perceive as distinct colors.

Surface treatment is inextricably linked to the way colors are perceived. Surface treatment should be considered in conjunction with color choice. The same color will look very different depending on whether the surface is metallic, brushed, anodized, transparent, translucent, etc.

With medical devices, surface treatment will affect how readily the product is able to be cleaned and disinfected. Fingerprints and smudges are readily seen on shiny, mirror surfaces, but too rough a texture will provide areas for contaminants to hide.

The Scale of the Product

Different color options are available depending on the size of the medical product you are designing. Large products will require a greater area of neutral color so as not to overpower the spaces in which they’re used. Smaller products such as hand-held tools and devices can, to a greater extent in their overall form, use colors that are darker, bolder and more saturated.

Choosing colors for large products is complicated by the fact that most color swatch samples are much smaller in relation to scale of the product. An identical color on a large object will look different than it will on a small object. To judge colors for large medical products, have candidate colors mixed in paint and apply the paint to 15”x20” (or larger) boards. Compare/judge the boards in the environment and under the lighting conditions that will be present where the product is used. You will get a much better idea of how the color will appear on the product than you will from a 1” color chip. The perception of color varies depending on the background against which it is viewed. That’s why it’s best to view the colors in an appropriate environment.

Branding

Color is one of the most powerful tools you can employ to develop a design language for a family of products. It will be one of the main elements that makes a particular device immediately identifiable as coming from your company. That’s a foundation upon which you can build, because branding is about establishing trust: if your products are trusted, your brand is trusted. Equally, if your brand is trusted, your products are trusted.

For medical products, employing color for branding purposes should be done strategically, with significant weight given to the functional and psychological characteristics of color that will be appropriate for the bulk of the company’s envisioned product offerings. The colors of the corporate logo might or might not be appropriate, depending upon all the other factors that go into making good color choices, as herein. Use corporate brand colors if you can, but don’t simply default to them.

The Effect of Environment on the Perception of Color

The colors of a product will be perceived differently depending on the environment the product is used in. The biggest factor will be the type of light it is seen under, and the lighting level. This is yet another reason that you should evaluate color choices by observing them in environment in which the product will be used.

Colors are not Seen in Isolation

Colors can seem different depending on the colors they are juxtaposed against. The perception of the color of the background changes also. This can be seen quite dramatically in what’s known as the Bartleson Brenneman effect:

In each row, the five squares are the same value. But their appearance changes depending upon the value of the background against which they’re viewed. This is also a good example of the effect of contrast. A dark background pushes all gray values toward white, while a light background pushes them toward black.⁽³⁾

Color Blindness

Approximately 8% of men and .5% of women are deficient in their color perception. It’s not that they can’t see any color at all (although for a very small segment, that is the case). It’s that they have difficulty distinguishing between certain colors. The most prevalent deficiency is red-green color blindness.

Ensuring there is sufficient value contrast is critical when designing for colorblind users. Red and green hues that are close in value won’t be able to be distinguished. However, if one of the hues is dark and the other light, the value contrast will be able to be seen⁽⁴⁾:

Where paying attention to red-green colorblindness is most important is when red and green are used as emergency signal cues.

Color Coding

Color coding is extremely important in medical devices. After value, hue is the distinguishing signal that is most quickly and efficiently processed by the brain.

According to the authors of Handbook of Human Factors in Medical Device Design, the most important factors to consider when using color for function coding are color choice, consistency, and number of colors. Per the handbook, red, green, yellow, orange and blue are the most easily recognized colors. Whichever colors are chosen, they should be used consistently throughout the product. The number of colors used for coding should be as few as possible (one color in addition to the base color that indicates user touch points, for instance, would be best). Numerous studies have found that we can only keep three or four pieces of information in our short term memory at one time. That would suggest that no more than four colors should be used for color coding.

Color coding should not be relied on as an exclusive cue. There should be a redundant signal as well (text, value difference, shape difference, etc.).

Biocompatibility

Some medical products will be required to have resin colorants that are biocompatible. A custom thermoplastics compounder will be able to provide colorants that have passed testing for FDA approval.

The Emotional Content of Colors

To a greater extent than we like to admit, our decisions are guided by emotion. Most of us probably believe that we rely predominantly on reason. But physiological and psychological processes of which we are largely unaware have a strong influence on how we think and on the conclusions of our consciousness. Of those things to which we react emotionally, color is at the top of the list.

When addressing color’s influence on emotion, you need to clearly understand what you want the overall impact of the design to be. Should it calm a patient? Should it seem intelligent and precise to a surgeon? Should it have a sense of fun about it so it’s less intimidating to a child in a pediatric setting?

Part of our emotional response to color has to do with the symbolism that certain colors have come to be associated with. Complicating things is the fact that symbolic associations differ among cultures, emotional effects differ among individuals, and color psychology is not a definitive science. Despite those caveats, certain colors do seem to evoke a more or less common response. You can use these to make purposeful color decisions:

White has a strong connotation of cleanliness/sterility and purity; therefore, it’s very appropriate in a medical setting. And because any color contrasts with white, using the neutrality of white for the bulk of the form allows you to easily use color to describe and draw attention to user input areas, thereby increasing the device’s usability, as mentioned above.
Light grey doesn’t have the pristine connotations that white has. But because white is so ubiquitous in medical settings, light grey can be a good alternative to make your company’s product distinct. Bright white can be overpowering and feel too sterile, whereas light grey is softer and calmer.
Blue has a soothing effect. It’s generally thought of as being the most serene and calming hue. That’s one of the reasons it predominates in medical device design. Green is also calming, and is associated with balance, harmony, and reassurance. Using soft tones of green or blue on accent areas of devices will make them feel less threatening – very appropriate in a clinical setting where the device is used to provide treatment to patients.
Black connotes seriousness, sophistication and excellence. It can be very effective for devices intended to be used in the laboratory. You need a compelling reason to use it in clinical settings though, because of black’s association with death.
Red is energizing. Because it’s a primary color, it can be appropriate in a pediatric setting. Its obvious association with blood makes it a color to avoid for devices used in the clinic, except in small amounts and for functional reasons to attract the eye to important areas:
Pink is a tranquil color. In Western cultures, it has obvious feminine associations, and should be employed with that in mind:
Yellow is sunny, optimistic and friendly. Great for pediatrics. Too much yellow can be overpowering though, so evaluate it carefully:
Orange is a happy color. As such, it can also be comforting. As with yellow, too much can be overpowering:
Brown is reliable and supportive in certain contexts, but its association with decay makes it a dubious color to use in medical devices.
Purple is associated with royalty, but also with religion and spirituality. As such, it could be used to provide reassurance to recovering patients. Lighter tints of purple are felt to be somewhat romantic, delicate and feminine. We are beginning to see purple being used more often in medical devices:

Violet is closely related to purple and carries with it some of purple’s connotations. Violet is considered to be serious and thoughtful. It’s a color that encourages contemplation, so it will have a quieting effect.

Summary

There are many factors that need to be considered when you are choosing appropriate colors to be used in the design of medical products. Understanding the user, understanding what the product needs to accomplish – not only functionally, but with a view toward the entire user experience – and understanding the context in which the product is used constitute the foundation upon which intelligent color choices can be made. Understanding how hue, saturation and value can be manipulated to change what a product communicates, and understanding the emotional and psychological content that different colors carry form a rationale for making deliberate color decisions.

The subject of color is rich and complex. It is also a powerful tool for design. I hope the information in this article helps you make deliberate, thoughtful and appropriate color decisions for the medical products and devices you will be designing in the future.

Webnotes

(1) http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2742127/

(2) http://www.colorsontheweb.com/colorterms.asp

(3) http://handprint.com/HP/WCL/color11.html

(4) http://designshack.net/articles/accessibility/tips-for-designing-for-colorblind-users/

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