The only color scheme I've ever noticed w/ clay bars is that blue ones are generally "normal use" clay bars that will not mar the paint if used properly and red ones are aggressive clay bars that pick up heavy contamination but are essentially like a super fine sandpaper in that they will mar the paint and require a followup polish.
I know a few websites that sell an "ultra fine" claybar that is usually white or yellow, but I don't see the point in getting it since a blue "fine" claybar will presumably remove more contamination and will not scratch if used properly.
Tecca, Clay Magic and Meg's still sell the red ones. They call it "medium grade." I actually have Clay Magic's red claybar... it's the only thing that I use to remove contamination on the notorious flat horizontal ledge at the bottom of the rear license plate opening. God, the contamination that builds there is terrible.
Last edited by nUcLeArEnVoY; 06-13-2013 at 10:44 AM.