I have seen the red ones, green ones, and blue ones. To be honest I don't know if one is better than another because they all share the same thing.They are Kevlar Cord belts.They are not supposed to stretch as much and supposed to be more durable.
Here is a insert I read earlier on them:
Martin Racing Performance, Inc :: Kevlar Belts
Made from the same material as bullet proof vests, this belt will eliminate slip as well as increase durability. As your stock belt wears down, it get thinner and thinner. This, in turn, will start to decrease your top speed. A Kevlar belt will keep this from happening.
So I take it that not only will you have less slippage and longer life but it's a good belt to have on if your riding your mower through a tough neighborhood?
Ted