User blog comment:DiegoAnime3000/Black is for Polarity/@comment-3146930-20140110104132

I think Weiss' Glyphs aren't polarity, but operate on similar Push/Pull physics. Generally when Weiss lands on one she is pushed in a certain direction to increase her speed or slow down falls. The Glyph only seems to turn black when she is charging up her Glyph for a stronger effect. This can be seen when holding Ruby for an extended period of time in the slingshot before finally launching her. This can also be seen when she is about to land the finishing blow to the boarbatusk, as she stays on that platform for a little extra time before launching forward. All her white Glyph platforms are normally used very quickly and could just be the default form. However the Red Glyph is never really explained. It could be that it was reacting to Ruby's semblance or possibly Red is the next step beyond Black; a much stronger Glyph that is about to become unstable.