The CMYK color model (process color, four color) is a subtractive color model, used in color printing, and is also used to describethe printing process itself. CMYK refers to the four inks used in some color printing: cyan, magenta, yellow, and key (black). Though it varies by printhouse, press operator, press manufacturer, and press run, ink is typically applied in the order of the abbreviation.
The "K" in CMYK stands for keysince in four-color printing cyan, magenta, and yellow printing plates are carefully keyed or aligned with the key of the black key plate. Some sourcessuggest that the "K" in CMYK comes from the last letter in "black" and was chosen because B already means blue. However, this explanation, althoughuseful as a mnemonic, is incorrect.
The CMYK model works by partially or entirely masking colors on a lighter, usually white, background. The inkreduces the light that would otherwise be reflected. Such a model is called subtractive because inks "subtract" brightness from white.
In additive colormodels such as RGB, white is the "additive" combination of all primary colored lights, while black is the absence of light. In the CMYK model, it is theopposite: white is the natural color of the paper or other background, while black results from a full combination of colored inks. To save money on ink,and to produce deeper black tones, unsaturated and dark colors are produced by using black ink instead of the combination of cyan, magenta and yellow.