Muckdrink Bog

You may tap a black or a green creature you control when Muckdrink Bog enters the battlefield, if you don't Muckdrink Bog comes into play tapped.
{t} : Add {b} or {g} mana to your mana pool.
It rains mud constantly as the muck drips down from the lake above, the vegetation has adapted to the like appearance of its water source.