In the context of a discussion of light (as opposed to pigments) complementary colours are two colours that, when mixed together, produce white light.

  • When working with the RGB colour model, combining the wavelengths corresponding with red, green and blue primary colours produces white for a human observer.
  • The complementary colour of each primary colour when working with the RGB colour model is the secondary colour produced by combining the other two primaries.
  • The complementary primary–secondary combinations of light are red–cyan, green–magenta, and blue–yellow.
  • Combinations of complementary primary–secondary colours at full intensity make white light because together they contain wavelengths corresponding with all three primaries.
  • A complementary colour plus a primary colour combine to produce white because each complementary colour is the product of combing two primaries.
  • So a complementary colour produced by combining green and blue primaries makes white when combined with red.