Additive colour

Additive colour refers to the way any two or more wavelengths of light can be combined to produce another colour. The RGB colour model and HSB colour model use additive methods to produce systematic ranges of colour.

Additive colour refers to the methods used and effects produced by mixing wavelengths of light.
Additive colour models such as the RGB colour model and HSB colour model can produce vast numbers of colours simply by adding red, green and blue lights together in different proportions.
An additive approach to colour is used to provide exact control over the appearance of colours on the digital screens of TVs, computers and phones.
Subtractive colour models such as the CMY colour model provide methods for mixing pigments such as dyes, inks or paints.
Both additive and subtractive colour models rely on mixing primary colours in different proportions:
- CMY refers to the primary colours cyan, magenta and yellow.
- CMYK refers to the primary colours cyan, magenta and yellow plus black (k).
- RYB refers to the primary colours red, yellow and blue.
Both additive and subtractive colour models can be explored using colour wheels.

About additive colour and the RGB colour model

The RGB colour model used by TV, computer and phone screens involves additive colour mixing. The RGB colour model produces all the colours seen by an observer simply by combining the light emitted by arrays of red, green and blue pixels (picture elements) in different proportions.

RGB colour is an additive colour model that combines 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 just these three component colours can produce any imaginable colour if mixed in the right proportion.
Different colours are produced by varying the brightness of the component colours between fully off and fully on.
When fully saturated red, green and blue primary colours are combined in equal amounts, they produce white.
A fully saturated hue is produced by a single wavelength (or narrow band of wavelengths) of light.
When any two fully saturated additive primary colours are combined, they produce a secondary colour: yellow, cyan or magenta.
Some implementations of RGB colour models can produce millions of colours by varying the brightness of each of the three primary colours.
The additive RGB colour model cannot be used for mixing pigments such as paints, inks, dyes or powders.

The RGB colour model does not define the exact hue of the three primary colours so the choice of wavelengths for each primary colour is the principal determinant of their admixture.
The RGB colour model can be made device-independent by specifying a colour profile such as sRGB or Adobe RGB (1998) which ensures consistent results regardless of the device used to output an image.