conditional formatting with dates

Hi people,
I need help with some conditional formatting formulas in excel.
What I have is a spreadsheet matrix showing a list of dates of when people passed
a test.
The formulas I need are for the cells to change colour as and when a certain
date is within range or has been reached (e.g Bob passed on 1-Jul-04), I need this
cell to highlight red when it is 3 years older (re-test date), yellow when within
30 days of re-test date and green up until any of the other two criteria is met.