Battlefield Forge

Oracle Text

T: Add C to your mana pool.

T: Add R or W to your mana pool. Battlefield Forge deals 1 damage to you.

Card Rulings

6/22/2015 The damage dealt to you is part of the second mana ability. It doesn’t use the stack and can’t be responded to.
6/22/2015 Like most lands, each land in this cycle is colorless. The damage dealt to you is dealt by a colorless source.