You should keep in mind that it is impossible to predict exactly how colors will be displayed and be perceived by someone viewing a digital image. This is important to keep in mind if you are developing multimedia materials that require learners to match colors from the real world to colors on a electronic display like a computer monitor (for example, matching shades and tints of green as a way to differentiate between leaves of different plant species). Although 8-bit displays (which is standard for modern monitors) can represent 16 million colors (8 bits per channel x three channels of red, green, and blue), there are many more colors than those 16 million, and these colors that cannot be displayed on computer monitors. Certain shades of brown and violet in particular cannot be displayed on a screen. In addition, monitor-specific settings (such as brightness and gamma) will alter the perception of colors on a screen. In MMS 151 (Web Accessibility), you will learn that not all people perceive color the same way because of color-blindness.

If color is important for performing critical tasks, remember these guidelines:

• Make sure that colors are perceived in the way you expect them to be perceived. To learn more about color perception and design, see, for example Ware (2004) or the writings of Edward Tufte.

• Don't expect users to be able make very fine-grained distinctions between many colors. For example, Figure 11.3 is mostly useless because few users can accurately match the colors.