Knowing CMYK basics in Photoshop

The CMYK color scheme is based on the light-absorbing quality of ink on paper. In theory, a white light hits these inks. Some visible wavelengths are absorbed, or subtracted, while others are reflected back to your eyes. CMYK images comprise various percentages of only four colors of ink — cyan, magenta, yellow, and black. These colors correspond to the inks used in the offset printing process.

Cyan, magenta, and yellow are called subtractive colors. Technically if you combine these three colors of ink, you produce black. But because of ink impurities, you actually end up with a nasty brown color. (That’s why we add K, or black to produce black.) CMYK colors are also known as process colors. Mixing colors in CMYK produces darker colors. Setting all four inks to 0% produces pure white.

Subtractive and additive colors are complementary. This means that each pair of subtractive colors creates an additive color and each pair of additive colors creates a subtractive color.