Whenever you cast a green creature spell, you may search your library for a creature card and reveal it. If you do, shuffle your library and put that card on top of it.
Whenever you cast a blue creature spell, reveal the top card of your library. If it's a creature card, put that card into your hand.
5/1/2006 If you cast a green and blue creature spell, both abilities will trigger. The abilities may be stacked so that when they resolve, you search your library for a creature card, put it on top of your library, and then put that card into your hand. The abilities may also be stacked in the other order, of course.