Editing Opponent process (section)

===Complementary colors===
{{main|Complementary colors}}
When staring at a bright color for a while (e.g. red), then looking away at a white field, an [[afterimage]] is perceived, such that the original color will evoke its [[complementary colors|complementary color]] (green, in the case of red input). When complementary colors are combined or mixed, they "cancel each other out" and become neutral (white or gray). That is, complementary colors are never perceived as a mixture; there is no "greenish red" or "yellowish blue", despite [[Impossible color#Colors outside physical color space|claims to the contrary]]. The strongest color contrast a color can have is its complementary color. Complementary colors may also be called "opposite colors" and are understandably the basis of the colors used in the opponent process theory.