Additive & subtractive colour

Additive colour is shorthand for the additive mixing of wavelengths of light to produce colour. The method involves mixing wavelengths corresponding with primary colours at varying intensities and projecting them onto a surface or screen. When seen by an observer, light enters and stimulates the eyes and, depending on the intensity of the signal on each channel, produces the visual impression of a predicted colour.

  • Whilst additive colour mixing is the method used to combine wavelengths of light, subtractive colour mixing is the method used with dyes, inks and pigments.
  • An additive approach to colour mixing is used in the case of the emission of light by light-emitting diodes (or similar light sources) embedded into the screens of mobile phones, computers and televisions etc.
  • An additive approach to colour mixing is also used with digital projectors. In this case, sufficient light must be produced on each channel to form intense images when focused onto a screen across a room.
  • RGB colour is one of the additive colour models that combine wavelengths of light corresponding with red, green and blue primary colours to produce other colours.
  • Red, green and blue are called additive primary colours in an RGB colour model because they can be added together to produce other colours. Red green and blue are often described as being components of the resulting colour.
  • Different colours are produced by varying the intensity of the component colours between fully off and fully on.
  • When fully saturated red, green and blue primary colours are combined, they produce white.
  • When any two fully saturated additive primaries are combined, they produce a secondary colour: yellow, cyan and magenta.
  • Some RGB colour models can produce over 16 million colours by fine-tuning the intensity of each of the three primary colours.
  • The additive RGB colour model cannot be used for mixing different colours of pigments, paints, inks, dyes or powders. To combine these colourants subtractive colour models are used.