Colour harmony is the idea behind why a certain colour scheme seems to fit the purpose of a room, a pleasant combination of colours. This is based on one or more of the following aspects:

- tone is a harmony using whites, greys and black.
- tone + chroma: used in a monochromatic colour scheme by varying the tone or chroma of one colour (different tints and shades of one colour).
- analogous harmony with a maximum of three adjacent colours in the colour wheel. (e.g. using red orange and yellow).
- complementary harmony is based on a good combination of two colors diametrically oppisite of the colour wheel. An important aspect is the amount of surface covered with the two colours: the warm colours (see colour contrast) are advancing colours, whereas the cold ones (like green and blue) are receeding. When you have a orange - blue room, the orange is the dominant colour. To make the room not too freaky, the amount of surface covered with orange has to be smaller than the blue objects, in a ratio of about 3.5:6.5 to create the harmony.
- light. Light influences the colour we think we see: a an object we call red actually absorbes the green light waves of the emission spectrum, hence relatively more red waves are reflected. There are four types of light: direct sunlight, North light, artificial incandescent light and fluorescent light (emits just a few specific wavelengths). By manipulating the type of light used, you can alter the colour of the object you see. Example: a room with a window facing north (northern hemisphere) has the natural North light, which is predominantly blue. To create warmth in a room you use blue-ish colours, because those objects absorb the blue, thuse relatively emitting more warm orange-like wavelengths; a balance in the "cold" room.

Back to colour theory.