Color Code Size for Searching Displays of Different Density

Twenty observers searched for three–digit numbers on displays ranging in density from 10 to 50 items coded in one through ten colors. Search times increased linearly with density and showed a curvilinear relation to number of colors used. An initial drop in search times as the first few colors were added to an uncoded display was followed by a rise in search times as still more colors were used. Minimal search times at different display densities were associated with different code sizes. Search times increased as more colors were added to the code, even when the number of items per color category was constant. The detrimental effect on search times of larger code sizes is interpreted as a camouflage of the color contour of the target's class by the multiple color boundaries in the heterogeneous background.