I've seen some people with different colored dark blast appearances. There are settings in the options menu that talk about the appearance of your dark blast and transparency, but they toggle whether other players should match your settings or not. I can't figure out where you need to go to actually modify your own dark blast. Can anyone shed some light on this? I tried the search function, but didn't get a whole lot of results, I presume because the function is new as of the most recent episodic release.
Derp. Start menu > Equipment > Dark Blast
I'd see about having the thread removed, but we'll keep it for posterity in case anyone else is as blind as me.