A developer colleague and I were discussing why it was bad practice to place red text (an error message) on a blue background. We then got on to the subject of what colours complement each other and I did a rather bad job of explaining basic colour theory. The book “Graphic Design – The New Basics” explains it well and I was excited enough with my new updated knowledge to dabble in a little colour exercises of my own.
Red, yellow, and blue. They can’t be mixed from other colours. All of the other colours of the colour wheel are created by mixing primary colours.
Orange, purple, and green each consist of two primaries mixed together.
Colours such as red orange and yellow green are mixed from one primary and one secondary colour.
Red/green, blue/orange, and yellow/purple sit opposite each other on the wheel. For more subtle combinations, choose “near opposites,” such as red plus a tertiary green, or a tertiary blue and a tertiary orange.
Colour schemes built from hues that sit near to each other on the colour wheel (analogous colours) have minimal chromatic differences.
[reference “Graphic Design – The New Basics”]
Colouring the web