That's crazy awesome!
The only thing that's kinda bugging me is the solid patches of yellow-orange around the white streaks... they kinda stick out more than the dithered areas... although I'm not sure how you'd change it.
Anyway, awesome work for only 15 colors!

EDIT: Okay, i think i see what's bugging me now:

The areas inside the blue look really blocky to me... I think just dithering them a bit would fix it up, though.
Also, the second-lightest white-orange color and the white-green colors are almost near invisible, and seem to just blend in with the solid white right now. I would darken the orange a tiny bit, and replace the light green completely with the same color in the flames and smoke. I'd change the green of the meteor to a different shade of green, as I couldn't see he color until I zoomed all the way in (might as well make it white/white-orange in its current state)
Hope that helps

Again, awesome job!