AB seems to be a bit dodgy with the backets in my reply (hence the missing end of my answers). I have uploaded a pic of the conditional formatting I use to achieve this, hopefully this will work!
So between 14 and 7 days beforehand, it shows blue, between 6 and 0 days before it shows green, and red for anything over. You can easily adjust the formulas for whatever limits you require. There's a minor error in the second formula (-7 instead of -6), but you should get the idea.