A secondary colour is created by mixing two primary colours in equal parts. The primary colours may belong to either an additive colour model, which combines wavelengths of light, or a subtractive colour model, which mixes pigments or dyes.
- In additive colour models such as the RGB colour model, which deals with the effects of mixing coloured light, a secondary colour results from overlapping the primary colours: red, green, and blue. The secondary colours produced by combining pairs of primary colours in the RGB model are cyan, magenta, and yellow.
- In subtractive colour models such as the CMY colour model, which is concerned with mixing dyes and inks, a secondary colour results from overlapping the primary colours: cyan, magenta, and yellow. The secondary colours produced by combining pairs of primary colours in the CMY model are red, green, and blue.