Game Plan

Assist allows another player to pay for any amount of generic mana. If an effect changes the cost of the spell, the amount that player may pay will be more or less than the amount in the spell’s reminder text.

Only the generic mana portion of a spell’s cost can be paid with assist. Any colored mana costs must be paid by the spell’s controller, even if the assisting player paid mana of that color.

If an effect allows a player to cast a spell spending mana “as though it were mana of any color” or “of any type,” that player must still pay for the colored mana in that spell’s total cost. That cost doesn’t become generic.