I haven't had the chance to watch too many games over the last few years, but here's my assessment on him in the limited time I've seen RS3.
I think he has a nice-looking, soft jumper. BUT, I have not seen him consistently make jump shots (in fact I've seen him airball several). He looks long, but he has slow feet so he can be a liability on defense despite his shot blocking ability.
A couple of years ago I thought Colt was a better post player. I didn't see as many games this last year so I'm not sure how they compare now. Too bad Colt left, but he'll do well at CSU. A RS year will be good for him.
I think it's great RS3 entered the draft for the experience, but another year in school would benefit him greatly.