Tetradic Colors

Tetradic colors are those that form a rectangle on the color wheel, and are also sometimes called rectangular colors.

In a tetradic color set there are two complementary color pairs rotated 60 degrees from each other. Not a description that does well with words so take a look at the image below. It makes more sense visually.

Tetradic colors on the color wheel
Tetradic Colors on the color wheel

Because tetradic colors are made up of complements it tends to be a very vibrant, although possibly jarring, color scheme. Care needs to be taken when using this scheme and it is best if one of the colors is dominant to the others.