CMYK color model

Color printing typically uses ink of four colors: cyan, magenta, yellow, and black.

When subtractive CMY inks are combined at full strength, pairwise combinations are red, green, and blue. Combining all three gives an imperfect black color.

What appears as cerulean ( ) in the top image is actually a blend of cyan, magenta, yellow and black, as magnification under a microscope demonstrates.

The CMYK color model (also known as process color, or four color) is a subtractive color model, based on the CMY color model, used in color printing, and is also used to describe the printing process itself. The abbreviation CMYK refers to the four ink plates used: cyan, magenta, yellow, and key (black).

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" the colors red, green and blue from white light; white light minus red leaves cyan, white light minus green leaves magenta, and white light minus blue leaves yellow.

In additive color models, such as RGB, white is the "additive" combination of all primary colored lights, and black is the absence of color. In the CMYK model, it is the opposite: white is the natural color of the paper or other background, black results from a full combination of colored inks. To save cost on ink, and to produce deeper black tones, unsaturated and dark colors are produced by using black ink instead of or in addition to the combination of cyan, magenta, and yellow.