Detection and Recognition of Colored Signal Lights

Two experiments were designed to determine effective colors for stimulus lights as measured by speed of detection and accuracy of identification, Additionally, the nature of the interactions between stimulus color, background color, and amount of ambient illumination were assessed. Responses to four stimulus lights, viz., red, green, yellow, and white, were evaluated against four colored backgrounds, viz., copper, tan, blue, and green, under two levels of ambient illumination. Responses of 144 subjects were also evaluated according to sex. It was found that to choose the most effective signal color in a specific situation, stimulus color, background, and amount of ambient illumination must all be considered. The overall ordering of stimulus colors as measured by speed of responding was, from fastest to slowest, red, green, yellow, and white. For errors in color naming, the order from least to most, was green, red, white, and yellow. Detection and identification were more difficult under bright ambient illumination. The addition of an identification task added about 0.25 sec. to the response times for each color.