What is CMYK?
The CMYK colour model (process colour, four colour) is a subtractive colour model, used in colour printing, and is also used to describe the printing process itself. CMYK refers to the four inks used in some colour printing: cyan, magenta, yellow and key (black). Though it varies by print house, press operator, press manufacturer, and press run, ink is typically applied in the order of the abbreviation.
The “K” in CMYK stands for key because in four-colour printing, cyan, magenta and yellow printing plates are carefully keyed, or aligned, with the key of the black key plate. Some sources suggest that the “K” in CMYK comes from the last letter in “black” and was chosen because B already means blue. Some sources claim this explanation, although useful as a mnemonic, is incorrect, that K comes only from “Key” because black is often used as outline and printed first.
The CMYK model works by partially or entirely masking colors on a lighter, usually white, background. The ink reduces the light that would otherwise be reflected. Such a model is called subtractive because inks “subtract” brightness from white.
In additive color models such as RGB, white is the “additive” combination of all primary coloured lights, while black is the absence of light. In the CMYK model, it is the opposite: white is the natural coluor of the paper or other background, while black results from a full combination of coloured inks. To save cost on ink, and to produce deeper black tones, unsaturated and dark colours are produced by using black ink instead of the combination of cyan, magenta and yellow.