Since Colorado law doesn't require firearm registration it would be in one's best interest to buy whatever and as much as they want that is currently legal. This includes currently legal magazines and ammo.
IMHO local jurisdictions would have even less ability than the State to try and enforce any new laws after the fact. Any newly prohibited items would have to be grandfathered in and wouldn't matter anyway. Unless everything is "date stamped" (like the failed attempt with MAGPUL) there is no case.
I'm sure a few places will attempt to exercise these new laws but they will be shown to be unenforceable as a solution where there wasn't a problem.