From M:TG Archive, a library of Magic: The Gathering information

Blue is the color of knowledge, illusion, reason, ingenuity, and trickery. Typical blue creatures include wizards, merfolk, and air spirits. Blue's cards are best at letting you draw additional cards; giving you control of opposing creatures; "unmaking" cards in play by returning them to their owner's hand; and cancelling your opponent's spells as they are being played. However, blue has by far the weakest creatures of any color, and it has only limited ways of dealing with opposing threats once they have entered play.