To reproduce full-color photographic images, typical printing presses use 4 colors of ink. The four inks are placed on the paper in layers of dots that combine to create the illusion of many more colors. CMYK refers to the 4 ink colors used by the printing press — the the subtractive primaries plus black.
C is cyan (a blue-green color), M is magenta (a reddish pink color), Y is yellow, and K is a pure black ink, the key plate or keyline color.
A mistake often made when submitting artwork for 4-color printing is not converting the images to the CMYK color space. This is needed so that the file can be separated into the four colors (see example) so that a separate printing plate can be made for each of the colors.
Also Known As: 4-color | process colors
Alternate Spellings: CYMK