RGB color model

RGB color model or RBG color standard (often spelled RBG in historical engineering literature) is an additive model in which red, green, and blue (often used in additive light models) are combined in various ways to reproduce other colors. The name of the model and the abbreviation ‘RGB’ come from the three primary colors, red, green, and blue and the technological development of CRTs which could display color instead of a monochrome phosphoresence (including grey scaling) such as black and white film and television imaging.

The term RGBA is also used, to mean Red, Green, Blue, Alpha. This is not a different color model, but a representation; the Alpha is used for transparency.

These three colors should not be confused with the primary pigments of red, blue, and yellow, known in the art world as ‘primary colors’, as the latter combine based on reflection and absorbstion of photons whereas RGB depends on emission of photons from a compound excited to a higher energy state by impact with an electron beam.

The RGB color model itself does not define what is meant by ‘red’, ‘green’ and ‘blue’ (specroscopically), and so the results of mixing them are not specified as exact (but relative, and averaged by the human eye).

When the exact spectral make-up of the red, green and blue primaries are defined, the color model would then become what is known in science and engineering as an absolute color space, such as sRGB or Adobe RGB; see RGB color spaces for more details.

This article discusses concepts common to all the different RGB color spaces that use the RGB color model, which are used in one implementation or another historically in color image producing electronics technology.