Primary colors and one woman at the corner

The opponent color theory suggests that there are three opponent channels: red versus green, blue versus yellow, and black versus white. Responses to one color of an opponent channel are antagonistic to those of the other color. The particular colors considered by an observer to be uniquely representative of the concepts red, yellow, green, blue, white, and black might be called "psychological primary colors", because any other color can be described in terms of some combination of these.

source: wikipedia