The colour theory developed by Itten is probably the best known colour theory among artists and designers. Based on Itten’s definition, I shall say that a set of colours is harmonious if the colours produce mid grey when they are mixed in equal quantities. A set of three colours is called a harmonious triad if it is harmonious according to this formal definition. Two colours are called complementary if they form a harmonious pair.
Itten also investigated unequal combinations of colours. He and many others have attempted to formalise some of these combinations in systems of colour schemes.
I don’t like that colour combination—Itten was very careful to distinguish individual subjective preferences from his generalised formal description of colour balance.
correctin some way. Just as artists and designers must decide whether a balanced composition is appropriate for a particular purpose, so they must decide whether to use combinations of colours that can be classified as harmonious or discordant. An unbalanced composition or discordant colours may produce precisely the tension that an artist is aiming for.