User blog comment:Zolnir/Virtual Reality/@comment-3146930-20140616204844/@comment-11188061-20140617011629

I've already mentioned it before but they are flames. Someone in the Chinese RWBY Tieba thread has already made the comparison with close up images and showed exactly what they are. The only one's that blurry is Blake's, but even in the Black Trailer all we can call it are 'black bubbles'.

In short,

Ruby - Rose Petals.

Yang - Yellow Flames.

Blake - Vanishing Bubbles.

Weiss - Snowflakes (literally).