the spectrum of light is made up of a combination of red orange yellow green blue indigo and violet. -If you shine a light through a prism it's split into it's seperate colours. This is what happens when you see a rainbow- it's the water in the sky/air acting as a prism. Black is a total lack of any colour being reflected, whereas when you see green you see green light reflected, red light reflected, etc etc. (that right?)
science lesson over
PS why is it not possible to get a totally white anno?