Gyro, Mechanical Magician

Whenever you cast a spell, You may play an instant or sorcery that costs X or less without paying it's mana cost, where X is the amount of colors you used to cast that spell.
{w}{u}{b}{r}{g},{t}: Exile ten Instants and Sorceries in your graveyard. Instants and Sorceries cost {0} until end of turn.