When we talk about risk in regard to usability, we usually center the conversation around the physical interaction with the device. User capabilities or disabilities, tactile functionality, device setup—all of these have a tangible impact on how the device is handled and used. However, multiple perceptive and cognitive forces behind usability can also have an effect. One that can get easily overlooked is color.
Intuitively, it may not appear as though color is a worthwhile consideration in relation to risk and usability; in many projects, it is a creative tag-on towards the end of development. But is it time to take it more seriously in our usability engineering efforts?
Perception of Color
How we perceive and react to color is integral to how it is used in device design. At a very basic level, product teams need to understand that even the very perception of color varies from person to person. This is influenced by many factors, including culture, experience, language, and variation in physical eye structure. Conditions such as color blindness also impact how color is perceived.
When using more than one color for the design, it’s important to consider the effect contrast may have. Placing two colors with low value contrast next to or on top of each other can impact the user’s ability to understand functionality or read necessary text. If the low contrast makes it difficult for a user to read something necessary for device interaction or delineate between interactive components, this could lead to use error and potentially a hazardous situation.
Understanding all these factors can inform how color can impact usability of a device. If a patient is color blind, will they be able to differentiate between buttons necessary for adjusting a device, turning it on, etc.? What if the color sends the wrong message? For example, the color yellow is used in many traffic signs to attract drivers’ attentions and encourage caution. The incorporation of a color (such as yellow) associated with caution but used in a non-cautionary way for a device component may discourage a user from interacting with it, even if it is integral to operation. If the user neglects to complete an interaction because of a color misperception, it has the potential to expose the user to a hazard. These basic perceptions need to be accounted for within the usability engineering process.
Color and Light in the Use Environment
The base level understanding of color perception is impacted in the usability engineering process by a very important factor: the use environment. Based on where and when a user is interacting with a device, perception of color can change. The largest variable within the use environment that will directly impact color perception is lighting—what type of light the device is being used under, and the lighting level itself.
For example, fluorescent bulbs produce different strengths and colors of light, depending on their use. Warm fluorescent lighting produces a different effect than “daylight” fluorescence, and each is used in an environment related to their purpose. On top of this, if lights have dimmers or are near the end of their usefulness, the quantity of light can vary within the use environment.
To illustrate how lighting as part of the use environment impacts color perception, recall the earlier discussion of low contrast. If two buttons on a device have separate functions but similar, low-contrast values, it’s plausible that the user’s perception of the buttons can change in a low-light environment. The contrast is less obvious in early morning or night settings, when light is less available, as well as environments with ineffective or varying artificial lighting. Morning sunlight, too, can cause the perception of a color to change as the low wavelengths of red, orange, and yellow light interact with the device interface. When interface features encounter that light, the confusion resulting in differentiating those features due to low value contrast has the potential to expose the user to hazards and harms.
Psychological Impacts of Color
While the research is still incomplete, there are links suggesting that our psychology and physiology are affected by color beyond just perception. Some studies point to how the color orange can make people hungrier, while blue subdues hunger. In drug research, scientists noted that participants associated drugs formulated with warmer colors (red, orange, yellow) with a stimulating effect; inversely, cooler colors (blues, greens, etc.) were associated with more “tranquilizing effects.” They theorized the relationship between the type of drug and its color impacted its perceived effectiveness.
The drug example isn’t directly applicable to medical devices, but it does provide some insight as to how the wrong color choice could inhibit use and impact effectiveness of treatment. For example, the color red is often associated with energy and power, and can potentially raise blood pressure. Red may therefore not be the ideal choice as the main color of a blood pressure device nor for device features, unless the color needs to contrast enough to draw attention to a meter, button, reading, etc.
Now, this sort of example seems low-risk at first glance, but it affects the device’s core functionality; if the color red has an impact on the user’s blood pressure, then, in theory, baseline readings and continued use will be inaccurate. This can lead to misdiagnosis and erroneous treatment. Whether the impact of the color red is statistically significant remains to be seen, but playing the example out can give us an idea of what the effects of color are to the patient and the risks that could ensue.
Device color design will almost always take a backseat to immediate, life-threatening risks identified in the design process. However, it should not be discounted entirely. Having a framework of the impacts of color in regard to usability and risk can help shepherd that part of the process through design phases with more ease.
To help product development teams through the color process, there are FDA and ISO guidelines that shed light on how regulatory bodies consider the use of color. For things like instruction manuals for devices, FDA recommends consistent use of colors when necessary but avoiding overuse, which could lead to confusion. ISO has pages of published standards about color coding on everything from dentistry devices to maritime equipment. Adhering to the guidance given by these regulatory bodies will help product development teams begin shaping their use of color with the user in mind.
The user is complex; many factors, including color, will influence them. Accounting for that early on in the design process will help avoid headaches in the long run.
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About the Author
Nick Schofield is a content creator for Cognition Corporation. A graduate of the University of Massachusetts Lowell, he has written for newspapers, the IT industry, and cybersecurity firms. In his spare time, he is writing, hanging out with his girlfriend and his cats, or geeking out over craft beer. He can be reached at firstname.lastname@example.org.