  the rgb color model is an additive color model in which red, green, and blue light are added together in various ways to reproduce a broad array of colors. the name of the model comes from the initials of the three additive primary colors, red, green, and blue. the main purpose of the rgb color model is for the sensing, representation, and display of images in electronic systems, such as televisions and computers, though it has also been used in conventional photography. before the electronic age, the rgb color model already had a solid theory behind it, based in human perception of colors. rgb is a device-dependent color model: different devices detect or reproduce a given rgb value differently, since the color elements (such as phosphors or dyes) and their response to the individual r, g, and b levels vary from manufacturer to manufacturer, or even in the same device over time. thus an rgb value does not define the same color across devices without some kind of color management. typical rgb input devices are color tv and video cameras, image scanners, video games, and digital cameras. typical rgb output devices are tv sets of various technologies (crt, lcd, plasma, etc.), computer and mobile phone displays, video projectors, multicolor led displays, and large screens such as jumbotron. color printers, on the other hand, are not rgb devices, but subtractive color devices (typically cmyk color model). this article discusses concepts common to all the different color spaces that use the rgb color model, which are used in one implementation or another in color image-producing technology. ==additive primary colors== thumb|additive color mixing: adding red to green yields yellow; adding red to blue yields magenta; adding green to blue yields cyan; adding all three primary colors together yields white. to form a color with rgb, three light beams (one red, one green, and one blue) must be superimposed (for example by emission from a black screen, or by reflection from a white screen). each of the three beams is called a component of that color, and each of them can have an arbitrary intensity, from fully off to fully on, in the mixture. the rgb color model is additive in the sense that the three light beams are added together, and their light spectra add, wavelength for wavelength, to make the final color's spectrum.{{cite book | title = digital video and hdtv: algorithms and
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