User blog comment:DiegoAnime3000/Black is for Polarity/@comment-15145664-20140110234404

I wholeheartedly agree with you. But, reather than be polarity as a whole (which will push or pull something depending on it's magnetic charge) I think it's exclusively a pulling force where as the color white is associated with a pushing force.

There's some evidence for this what with Weiss using white glyphs to increase her speed, and as walls and platforms to jump from

The only bug with this theory however is actually found in the Red trailer. Ruby uses bullets that give a white muzzle flash, right? it fits for those bullets being stronger since they're enhanced with white dust, but then she switches to different bullets with a black muzzle flash. Wouldn't that mean that her bullets are now using black dust?

I've thought about this a lot and I don't know what to make of it. But, I do think that black is meant to represent gravity and magnetism