CMYK refers to the four inks used in color printing: cyan, magenta, yellow, and key (black). The CMYK model works by partially or entirely masking colors on a lighter, usually white, background. The ink reduces the light that would otherwise be reflected. Such a model is called subtractive because inks “subtract” brightness from white. The RGB color model (website display) is an additive color model in which red, green and blue light are added together in various ways to reproduce a broad array of colors.