Successive Contrast

Stare at the muli-colored circle below for about twenty seconds, and then look at the center of the white circle at left. Complementary afterimages should begin to bloom on the white circle. The blue sector at the bottom becomes yellow. Green changes to magenta, and cyan changes to red.

Repeat the same experiment, staring first at the center of the multicolored circle for twenty seconds. This time shift your gaze to the cyan circle at right. Perhaps you will notice that the afterimages now change your perception of each of the cyan sectors. Which sector appears the most intense version of cyan? 

Most people report that the strongest cyan appears where the red sector had been. This is called successive contrast. When you look at an object of a certain color, your eyes adjust or adapt to that color. The resulting afterimage affects what you look at next. 

This is why providing strategic areas of complementary colors helps enliven a color scheme. In this painting by Thomas Moran, for example, the strong chromatic effect of the orange cliffs is heightened by the proximity of complementary colors at close values. 

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From "Color and Light: A Guide for the Realist Painter."