Design: Colour scheme definitions

I found the following definitions of different colour schemes, adapted from this tutorial, really useful and wanted to note it here for future use.

Monochromatic - uses multiple shades of one colour. Shades of gray are considered achromatic as they don't actually contain colour. It's pretty much the same thing though.

Analogous - uses colours adjacent to one another on the colour wheel. Apparently this can be tricky: choosing colours further apart than 1/3 of the wheel can result in less appealing combinations.

Complementary - uses colours on opposite sides of the colour wheel. Something to watch for here is simultaneous contrast, where the colours enhance one another to the extent that they become difficult to look at and possibly even illegible.

Split Complementary - uses two colours adjacent to the complimentary colour of your base colour. Or something.

Triadic  - uses three colours 1/3 of the colour wheel apart from one another.

Tetradic - uses four colours made up of two complimentary pairs.

To see some of these schemes in action, check out the Color Scheme Designer.