Reading about the rulings for Gilded Lotus, I've discovered that "add three mana of any one color" means: add three mana of a single color, not three mana of possibly distinct colors.
Black Lotus' text reads exactly the same. This means the widely known one-turn win consisting of Fireball, Channel and Black Lotus could not possibly work, since Black Lotus alone could not provide {R}{G}{G}.
Is this actually correct? Did the rule over this change?