User blog comment:DiegoAnime3000/Black is for Polarity/@comment-15145664-20140110234404/@comment-3257939-20140111194526

My head hurts, sorry, I really don't see your point. Weiss used the Black Glyph to pull herself and prepare to strike, then, when she was ready, she launched herself against the Grimm once the Glyph was blue.

I don't understand about White being anti-gravitational force and how you got that idea? It's simple, she used black to pull herself and Ruby, then, changed the color to launch. Polarity is control over magnetism, something Weiss knew well when Ruby failed to understand. And the White Glyph is something only for the trailer, it hasn't been used during the series. Maybe Monty changed that because the idea of Dust was recently created and there was still work to do on how it works, or it was all in Weiss' head.

She used black to pull things because it's a Glyph, Pyrrha moved things because it's her semblance and she has a greater control over it, she can do it at distance but Weiss can only do it in a certain area because it's an motionless Glyph.