I picked up Super Stardust HD as part of the PSN's "Welcome Back" package a few months ago, but I didn't have a proper go at it until yesterday.
The game informs you early on that the three weapon types you posses are effective when trying to breakdown specific types of meteors (rock, gold and ice). However, the game's help hints that weapon vulnerabilities can be discerned from the color of what you are shooting at (green for rock smasher, red for gold cutter and blue for ice melter).
While all enemies I've come across so far are indeed color coded, I can't say I've noticed them dying more quickly based on my weapon selection. Then again, the game is pretty hectic so I can't say I've been able to experiment.
So are enemies really more vulnerable to the weapon corresponding to their color? What about bosses (The first boss has blue colored weak-spots)?