A card with devoid is colorless. But is it still colorless when it's a spell? I mean: when is it in the stack, that is, when it is not yet a permanent, and when it has not yet been resolved?
As an example, I can take a card called Unnatural Aggression (mana cost 2G,so that at first glance it may seem that the spell is green). Is it possible to choose as one of this spell's targets a creature that has "protection from colored spells" among its abilities?