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RGB color spaces are a category ofadditive colorimetriccolor spaces^[1] specifying part of its absolute color space definition using theRGB color model.^[2]

RGB color spaces are commonly found describing the mapping of the RGB color model to human perceivable color, but some RGB color spaces use imaginary (non-real-world) primaries and thus can not be displayed directly.

Like any color space, while the specifications in this category use the RGB color model to describe their space, it is not mandatory to use that model to signal pixel color values. Broadcast TV color spaces likeNTSC,PAL,Rec. 709,Rec. 2020 additionally describe a translation from RGB toYCbCr and that is how they are usually signaled for transmission, but an image can be stored as either RGB or YCbCr. This demonstrates using the singular term "RGB color space" can be misleading, since a chosen color space or signaled color can be described by any appropriate color model. However the singular can be seen in specifications where storage signaled as RGB is its intended use.

The normal human eye contains three types of color-sensitivecone cells. Each cell is responsive tolight of either long, medium, or shortwavelengths, which are generally categorized as red, green, and blue. Taken together, the responses of these cone cells are called theTristimulus values, and the combination of their responses is processed into the psychological effect of color vision.

RGB use in color space definitions employ primaries (and often awhite point) based on the RGB color model, to map to real world color. ApplyingGrassmann's law of light additivity, the range of colors that can be produced are those enclosed within the triangle on the chromaticity diagram defined using the primaries asvertices.^[3]

The primary colors are usually mapped toxyY chromaticity coordinates, though theuʹ,vʹ coordinates from the UCS chromaticity diagram may be used. Both xyY and uʹ,vʹ are derived from theCIE 1931 color space, a device independent space also known asXYZ which covers the fullgamut of human-perceptible colors visible to theCIE 2° standard observer.

RGB color spaces are well-suited to describing the electronic display of color, such ascomputer monitors andcolor television. These devices often reproduce colors using an array of red, green, and blue phosphors agitated by acathode-ray tube (CRT), or an array of red, green, and blueLCDs lit by a backlight, and are therefore naturally described by an additive color model with RGB primaries.

Early examples of RGB color spaces came with the adoption of theNTSC color television standard in 1953 across North America, followed byPAL andSECAM covering the rest of the world. These early RGB spaces were defined in part by the phosphor used by CRTs in use at the time, and the gamma of the electron beam. While these color spaces reproduced the intended colors using additive red, green, and blue primaries, the broadcast signal itself was encoded from RGB components to a composite signal such asYIQ, and decoded back by the receiver into RGB signals for display.

HDTV uses theBT.709 color space, later repurposed for computer monitors assRGB. Both use the same color primaries and white point, but different transfer functions, as HDTV is intended for a dark living room while sRGB is intended for a brighter office environment.^{[citation needed]} The gamut of these spaces is limited, covering only 35.9% of the CIE 1931 gamut.^[4] While this allows the use of a limited bit depth without causingcolor banding, and therefore reduces transmission bandwidth, it also prevents the encoding of deeply saturated colors that might be available in an alternate color spaces. Some RGB color spaces such asAdobe RGB andProPhoto intended for the creation, rather than transmission, of images are designed with expanded gamuts to address this issue, however this does not mean the larger space has 'more colors". The numerical quantity of colors is related to bit depth and not the size or shape of the gamut. A large space with a low bit depth can be detrimental to thegamut density and result in high${\displaystyle \mathrm{\Delta }E}$ errors.^{[further explanation needed]}

More recent color spaces such asRec. 2020 for UHD-TVs define an extremely large gamut covering 63.3% of the CIE 1931 space.^[5] This standard is not currently realizable with current LCD technology, and alternative architectures such asquantum dot^[6] orOLED^[7] based devices are currently^[when?] in development.

TheCIE 1931 color space standard defines both the CIE RGB space, which is a color space with monochromaticprimaries, and the CIE XYZ color space, which is functionally similar to a linear RGB color space, however the primaries are not physically realizable, thus are not described as red, green, and blue.

M.A.C. is not to be confused with MacOS. Here, M.A.C.refers toMultiplexed Analogue Components.

• CIELUV color space
• Web colors
• RGB color model
• RGBA color model

• RGB Color Chart.
• "Three component color encoding registry". International Color Consortium (ICC). Retrieved2022-02-11.
• Susstrunk, Buckley and Swen."Standard RGB Color Spaces". Archived fromthe original(PDF) on February 17, 2007. RetrievedNovember 18, 2005.
• Lindbloom, Bruce."RGB Working Space Information". RetrievedNovember 18, 2005.
• Colantoni, Philippe."RGB cube transformation in different color spaces". Archived fromthe original on 2008-05-05.

• Color space

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