a.k.a. Cyan, Magenta, Yellow, BlacK. The color model in which all colors are described as combinations of these four colors. Most color printers, ink-jet, laser, dye-sublimation, thermal, and crayon printers use these as their printer colors. One of the biggest challenges of desktop publishing is color matching because the conversion from RGB to CMYK can cause color shifts - making it difficult to match the print with what is on your monitor.