Conditional formatting - job completion status by colour

I've had problems formatting in Excel. Can anyone suggest a suitable video? Or better, even outline steps to do the following:

I'm trying to flag employee task completion status by automatically showing background fill:
LESS THAN 5 days is GREEN.
MORE THAN OR EQUAL TO 5 days, but LESS THAN 10, turns YELLOW.
MORE THAN OR EQUAL TO 10 days, turns RED.

I don't need to differentiate types of day (weekends,etc), but I do need to show dates, not just codes. And I need a historical record for several months before clearing and starting fresh.

Eg, assuming today is 27 Nov 2011:
EmpA is GREEN because she completed in LESS THAN 5 days.
EmpB is RED because she completed IN MORE THAN OR EQUAL TO 10 days.
EmpA (second task) is GREEN because she still has a few days left.

A B C D
1 Employee Task Assigned Completed
2 EmpA 11e02 22 May 2011 25 May 2011
3 EmpB 11e82 26 May 2011 15 Jun 2011
4 EmpA 11e03 25 Nov 2011 pending

Any help would be much appreciated.