Yea. It isn't worth messing with. AZ was very lenient. CO requires the light.
"Either a tail lamp or a separate lamp shall be so constructed and placed as to illuminate with a white
light the rear registration plate and render it clearly legible from a distance of fifty feet to the rear. Any
tail lamp or tail lamps, together with any separate lamp for illuminating the rear registration plate, shall be
so wired as to be lighted whenever the head lamps or auxiliary driving lamps are lighted."
Looks like I will run something compatible and clean on the bike.