At the beginning of each player's upkeep, that player chooses a color. Until end of turn, lands tapped for mana produce mana of the chosen color instead of any other color.
Legalities
Legal
Duel
Predh
Legacy
Vintage
Commander
Premodern
Oathbreaker
Not Legal
Brawl
Penny
Future
Modern
Pauper
Alchemy
Pioneer
Explorer
Historic
Standard
Timeless
Gladiator
Oldschool
Standardbrawl
Paupercommander
Rulings
2016-08-23
Any colorless mana that's produced isn't affected.