Complementary colours

In the context of a discussion of light, complementary colours are pairs of colours that, when mixed together, produce white and when placed next to each other appear to create the strongest possible contrast.

In the context of a discussion of paints and inks, complementary colours are pairs of colours that, when mixed together, produce a brown-purple-black colour and when placed next to each other appear to create the strongest possible contrast.

  • Complementary colours are colours that when compared with one another appear to be in complete contrast with one another when viewed by an observer.
  • Pairs of complementary colours always involve a primary colour and a secondary colour. The secondary colour is the one that can be produced by mixing the other two primaries.
  • Combinations of two complementary colours of light at full intensity produce white.
  • Combinations of two complementary paint colours in theory produce black, but mixing pigments is not straightforward, so usually results in a brown-purple-black colour.
  • Complementary colours always juxtapose one cool colour with a warm colour. Reds, oranges and yellows are the warm colours, while blues, greens, and purples are the cool colours.

Summary

About complementary colours and colour wheels
  • Complementary colours are always opposite one another on a colour wheel.
  • The complementary colour of a primary colour is always a secondary colour on a colour wheel.
  • The pairs of primary and secondary colours that produce complementary colours depend on the colour model:
    • When mixing light (using an additive colour model) the pairs are red-cyan, green-magenta and blue-yellow
    • When mixing pigments (using a subtractive colour model) the pairs are red-green, yellow-purple and blue-orange
    • In the case of digital printing (using a subtractive colour model), the pairs are cyan-red, magenta-green and yellow-blue
  • The intermediate colours between three tertiary colours on a colour wheel always include one primary and two secondary colours. Adding the two secondary colours together produces the complementary of the primary.
About complementary colours and the RGB colour model
  • When using the RGB colour model, the primary/secondary pairs of complementary colours are red-cyan, green-magenta and blue-yellow.
  • Combining the wavelengths corresponding with all three RGB primary colours produces the impression of white for a human observer.
  • When working with the RGB colour model the secondary colour that pairs with any primary colour is produced by mixing the other two primaries together.