Rainbow Dragon

As an additional cost to cast Rainbow Dragon,
in your graveyard or on the battlefield under
your control you must have a red permanent,
a green permanent, a blue permanent, a black permanent, a white permanent, a colorless
permanent with {c} in its mana cost and a
colorless permanent without {c} in it's mana cost.
At any time while on the battlefield Rainbow
Dragon may gain a keyword of your choice until
the end of the turn. Limited 1