Why can't I find a color changing GU24 bulb?
GU24 to Edison Screw adapters are absolutely fine provided they are rated for the electrical load you will be putting through them, and designed for heat resistance. Most I've seen are rated up to 150 watts, which is far more than you need - most LED bulbs are 10 watts maximum. So get good quality adapters and you'll be fine. Keep in mind that these adapters could make the bulbs stick out a bit.