Creature — Ooze 1/1, R (1)
Rare
At the beginning of your upkeep, if you control a black permanent, you may put a +1/+1 counter on Bloodhall Ooze.
At the beginning of your upkeep, if you control a green permanent, you may put a +1/+1 counter on Bloodhall Ooze.
A drop of blood spilled from the first dragon.
Illus. Jaime Jones

2/1/2009: The "intervening 'if' clause" means that (1) the ability won't trigger at all unless you control a permanent of the specified color, and (2) the ability will do nothing unless you control a permanent of the specified color at the time it resolves.
2/1/2009: A permanent that's both black and green will allow both abilities to trigger (as will separate black permanents and green permanents, of course).
Legal in Vintage (Type 1)
Legal in Legacy (Type 1.5)
Legal in Classic (MTGO)
Legal in Commander
Legal in Modern