CMYK is the subtractive color model that uses cyan, magenta, and yellow as primary colors. CMYK stands for cyan, magenta, yellow, and key (black) colors. The "key" color can be whatever ink plate provides the most detail to the printed image. If black ink is not being used, another color can take the "key" position.

The CMYK color model is used in four-color process printing. You can produce virtually any color in the visible spectrum by adding these four colors together in varying ratios.