Conditional Formating with dates

I am trying to automatically highlight cells where the date in the cell falls within certain criteria.

Example: A report was received on Date "A". The due date is "B". I am trying to auto fill the cell with color if the date is 1-2 months past B, 3-5 Months past B, and 6+ months past B. For the life of me I cannot figure out how to do this.