Blue is the color of intellectualism and prioritizing logic. By its nature, blue is prone to being good at strategy. Magic is a strategy game, so it makes sense

Blue is the color of intellectualism and prioritizing logic. By its nature, blue is prone to being good at strategy. Magic is a strategy game, so it makes sense blue is inherently good at it. And that's a bit tongue in cheek, but in all seriousness blue is the color of mind tricks and the hacker mentality, so it makes sense blue prefers manipulating game state in ways other colors just won't think of doing, and unfortunately the game's designers grossly underestimated just how powerful "manipulating game state" is.