Achromatic - colour scheme that uses no colours, only black, white and greys.
Monochromatic - colour schemes that use tints, tones and shades of only one colour.
Analagous - colour scheme that uses different tins, tones and shades of three or four colours that are next to each other on the colour wheel.
Complementary - colour scheme that uses tints, tones and shades of a colour and its complement.
So, as you can see, I haven't totally been slacking off! I hope that I will finally get a handle on this colour theory now and be able to use it effectively in my stitching.