Colors which, when mixed in varying proportions, will yield a perception of all other colors. The technology of cathode ray tubes (CRTs) uses the additive primaries of Red, Green and Blue. They are called additive because one starts with an absence of light (black) and progressively adds various combinations of the three primaries. In the additive system, red and blue combine to form magenta, blue and green combine to form cyan, and red and green combine to form yellow. All three additive primaries combined together form white_x000D_
Most printing devices use the subtractive primaries of Magenta (Red-Blue), Cyan (Blue-Green) and Yellow (Red-Green). They are called subtractive because the inks act as filters which subtract out particular wavelengths. Thus starting with all possible wavelengths combined , the primaries are mixed to subtract out particular wavelengths and leave the color desired. In the subtractive system, magenta and cyan produce blue, magenta and yellow produce red, cyan and yellow produce green, and all primaries mixed together produce black.