For my chemistry notes I needed a colour wheel which can be used to work out the colour of a pigment or dye when the wavelengths at which light is absorbed are known or to work out the wavelengths that are absorbed on when the colour is known.
The opposite colour across the wheel is the complementary colour. A red pigment absorbs green light. A dye that absorbs yellow light appears violet.
I coloured in the diagram linked to below using gimp.
The original diagram
This continues my series of educational resources. Google did not find what I was looking for straight away, hopefully now it will.