Maavis, Chroma Mage

Maavis enters the battlefield with three +1/+1 counters on him.
Whenever you cast a spell, if it doesn't share
any colors with permanents you control, draw
a card.
{1}{u}, Remove a +1/+1 counter from Maavis:
Choose a color. The next spell you cast this
turn is that color instead of its other colors.