The Red Horse is an animal in Farmville. It is only available via the Zynga Lotto.
You can get 1 from friends who finished Horse Paddock quest Sugar High.
On September 28th, 2011 for short time (under hour) show up glich that allowed buying this horse from market for 2,500 coins. It was visible after entering "Red Horse" in market search field. This glich was fast patched.