Emissary's Ploy

(Start the game with this conspiracy face up in the command zone.) Before drawing your opening hand, choose 1, 2, or 3. You may spend mana as though it were mana of any color to cast creature spells with mana value equal to the chosen number.

From Magic: The Gathering.

Open the interactive version on https://mythscribe.cloud/app/tcg/cards/cms6oml8kgh0jpb1h68basbzw.