The act of decomposing a color graphic or photo into single-color layers. For example, to print full-color photos with an offset printing press, one must first separate the photo into the four basic ink colors: cyan, magenta, yellow, and black (CMYK). Each single-color layer is then printed separately, one on top of the other, to give the impression of infinite colors.
This type of color separation, mixing three or four colors to produce an infinite variety of colors, is called process color separation. Another type of color separation, called spot color separation, is used to separate colors that are not to be mixed. In this case, each spot color is represented by its own ink, which is specially mixed. Spot colors are effective for highlighting text but they cannot be used to reproduce full-color images.