Color theory has long had the goal of predicting or specifying the color combinations that would work well together or appear harmonious.

The color wheel has been adopted as a tool for defining these basic relationships.
Some theorists and artists believe juxtapositions of complementary colors are said to produce a strong contrast or tension, because they annihilate each other when mixed; others believe the juxtapositions of complementary colors produce harmonious color interactions.
Colors next to each other on the color wheel are called analogous colors. They tend to produce a single-hued or a dominant color experience. Harmony has been sought in combinations other than these two. A split complementary color scheme employs a range of analogous hues, "split" from a basic key color, with the complementary color as contrast. A triadic color scheme adopts any three colors approximately equidistant around the hue circle. Printers or photographers sometimes employ a duotone color scheme, generated as value gradations in black and a single colored ink or color filter; painters sometimes refer to the same effect as a monochromatic color scheme.