CS 552, Spring 1998
Color Coding Guidelines
Derived from Richard E. Christ, 1975, "Review and Analysis of Color Coding
Research for Visual Displays," Human Factors, Vol. 17, No., 6, pp.
(1) Avoid "false coding," where the association of particular
colors implies relationships that do not actually exist.
- Explanation: Some colors have
emotional associations that should not have to be un-learned.
Avoid their use in arbitrary contexts, so as not to
confuse and frustrate users.
- Example: Red/yellow/green should not be used to identify
qualitative groups (e.g, democrats vs. republicans vs.
- Exception: "False code" colors can be included as part
of a broader spectrum of colors, since the association will be
(2) Use the four "focal colors" to encode information that needs to be
- Explanation: The focal colors (red/blue/yellow/green) are
easily discriminated, and unlikely to be confused with one
another. They are also easily remembered and recognized
by individuals from most cultures.
- Example: For a series of related graphs or other images
than encode information (e.g., maps showing different densities,
bar charts comparing values from different subsets of a population)
use these colors so that the user can quickly distinguish
the values for each subset.
- Exception: Be careful not to imply a false relationship
among red/yellow/green. If there are three values to be
coded, deliberately choose blue as one of them to break the
cultural associations with red/yellow/green.
(3) Avoid subtle distinctions in color codes.
- Explanation: The difference between to similar colors
may be discriminable when the colors are adjacent, but will
easily be lost when colors are intermittent in a display.
The difference between perception and reality means that
a users may not see the color correctly, or may "see" a
color that isn't really there.
- Example: Colors that are close to each other (e.g., red
and orange of a similar brightness and intensity) are easy
to confuse when they are not adjacent to one another. If
they must be used, vary the colors along multiple dimensions,
changing the brightness and intensity as well as hue (e.g.,
bright red but pale orange).
- Exception: A closely related spectrum may be desirable
to indicate subtle variations in values, such as a map
showing temperature gradations. Beware that users may
misinterpret particular values, however.
Prepared by C. Pancake, March 31, 1998