Whitemane Outrider

Manashift {2}{g}{g} (You may cast this spell for its Manashift cost. If you do, it becomes green and loses all other colors.)
When Whitemane Outrider enters the battlefield, if it's white, create a 2/2 white Cat creature token.
Was long as Whitemane Outrider is green, it gets +2/+2 and has trample.