Buy a few receivers of any type, AR, AK, whatever, in general they are cheap and you can always buy the rest of the kit later to get built up.
In general though the new Colorado law still allows you to buy these firearms if you go through the safety course. I had to do this to get my carry license renewed this past year. It was a joke. Basically pay $100 to sit through a class where the answers to the test are given to you as you take the test.
Either way it's an infringement of a right and shouldn't exist. The Mountain States Legal Foundation has been pretty successful with fighting these bills and they have already filed a suit against this particular bill. They recently got New Mexicos waiting period thrown out.