The CMYK color model (process color, four color) is a subtractive color model, used in color printing, and is also used to describe the printing process itself. CMYK refers to the four inks used in some color printing: cyan, magenta, yellow, and key (black). Although it varies by print house, press operator, press manufacturer, and press run, ink is typically applied in the order of the abbreviation.

Four color process printing is a system where a color image is separated into 4 different color values (called a color separation) by the use of filters and screens. This used to be done with photographic film on a graphic arts camera, but is usually done digitally with software now. The result is a color separation of 4 images that when transferred to printing plates and sequentially printed on a printing press with the colored inks cyan (blue), magenta (red), yellow and black (the k in cmyk), reproduces the original color image.