Design of information Display Systems for Air Traffic Control - FAA

3.3 Other Topics
3.3.1 Use of Color
Color can be an extremely effective cue for highlighting information, drawing the user’s
attention, reducing clutter, or grouping similar elements (HF-STD-001, 8.6.2.1). If used
improperly, however, color can lose its effectiveness at drawing the user’s attention and can add
clutter and noise to a display. We describe some general guidelines for the use of color here. A
more comprehensive set of guidelines is available in the Human Factors Design Standard (HF-
STD-001, 8.6.2) as well as in other sources (e.g., Cardosi & Hannon, 1999).
Color should be used conservatively and consistently. Color should be used to designate
meaningful categories of displayed information if it will facilitate user understanding or
performance (HF-STD-001, 8.6.2.7.1). Because only eight or nine highly saturated colors can be
easily discriminated, the total number of colors used should not exceed four for a single display
and seven for a set of related displays (HF-STD-001, 8.6.2.7.3). Additional colors should be
reserved for special use (for example, in map displays) (HF-STD-001, 8.6.2.7.4).
Although users often express a preference for color, it does not always improve their
performance (HF-STD-001, 8.6.2). If used to represent meaning, each color should only
represent a single category of information (HF-STD-001, 8.6.2.4.1). In the field, we observed
some IDSs that successfully used color to organize the display and to draw the user’s attention to
information that was relevant to their tasks. We also observed displays that appeared noisy due
to the use of too many colors or inconsistent application of meaning to color.
The issue of color selection is complex and very important. The use of color should not reduce
the readability of information on the display (HF-STD-001, 8.6.2.1.7). Therefore, colors should
be selected carefully for the display of information, particularly for combinations of text and
background. Readability should be evaluated with users under operational conditions such as
ambient lighting and display type (HF-STD-001, 8.6.2.5.3). If multiple colors are used to
represent categories of information, they should be distinguishable under operational conditions
(HF-STD-001, 2.6.9). It is also important to be aware of existing color-coding conventions and
reserved meanings, such as the use of red for emergency or failure conditions. In Figure 10 for
example, red is only used for the emergency checklist button and to highlight closures.
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