CMYK is a subtractive color model that is used in color printing, and it refers to cyan, magenta, yellow, and black for the inks used in color printing. The “K” in CMYK is understood to be the key since in four-color printing cyan, magenta, and yellow printing plates are aligned with the black plate which is the key. In other words the other colors are setup in relation to the black which is thus the key to the process. The fact that it is subtractive means that in the CMYK process the color results are achieved by masking colors on a lighter background.