The CMYK system consists of the primary colours cyan, magenta and yellow. Again, the initials make up the name of the system.

However, these three colours only give us the first three letters of the name (CMY). The fourth letter, K, stands for key (black), and is used to shade the colour (or to print pure black).

Black is needed because cyan, magenta and yellow don't form a perfect black, rather a dirty-looking brown.

White can not be printed in the subtractive colour model CMYK. It is produced by not printing anything onto white paper.

The CMYK system has long been the standard model for process color. The values don't range from 0 - 255 (as in RGB), but are percentages from 0% - 100%, which make up the tonal values.