Colour wheel
Use a colour wheel to help plan the overall scheme of a room.
Primary colours are three key colours - Red, Blue and Yellow. They cannot be made from any other colour.
Secondary colours
If you mix equal amounts of the primary colours, you get the Secondary colours - Purple, Green and Orange.
Red + Yellow = Orange
Red + Blue = Purple
Blue + Yellow = Green
Tertiary colours
If you mix a primary with a secondary colour, in a ratio of 2:1, you get a Tertiary colour. Red-Orange, Blue-Green etc.