Primary colors are the root of every other color. They are impossible to form by blending other hues. In the subtractive color model (used in printing, silk-screening, and painting), primary colors include cyan, magenta, and yellow. In the additive color model (used by digital displays), they are red, green, and blue.

In design, primary colors have a powerful visual and psychological impact. They're often used as accent colors in their pure forms so they're not overpowering. However, leaning more heavily on primary colors would be the way to go when you want to make an impact.