Changing color in cells based on values in different cells

Hey,

I have two different cells containing either "OK1" or "OK2"

I would like to change a third cell into the color red if both cells ar "OK2", orange if one of the cells is"OK2" and green if both cells is "OK1".

I tried solving this problem using conditional formating, but couldn't get it to work when checking a value on a different cell. Is it possible to trig cell color using IF-sentences?

Ant tips?