Contrast is crucial. Colours must be far enough apart on the colour wheel to allow the eye to easily discern the elements on a page.
Nowhere is sharp contrast more important than between the background and text.
Use dark font colours on light backgrounds, and vice versa.
Just like writing for the web, keep it simple where text is involved. Avoid patterns behind text. And if a page is going to be printed, avoid using a dark background colour.
Limit your use of colours. Twenty different colours on a page will probably look like a mess - and it will be confusing. Some experts suggest no more than five colours.
Avoid red/green combinations to avoid problems for colour blind people. (Did you know that approx. one in 10 men is colour blind?)
Avoid reversing white text out of a black background.
Choose brighter colours for older people.
Test with a range of people across gender and age groups. Also test your colours under different light conditions.