Almost never see it on the front range of CO, nor in the mountains. Go to a Walmart on the western slope or wyoming and there's almost always someone open carrying. It's not my jam, but outside of denver itself it's entirely legal (as it should be). I will say though, somehow it's always "that guy" open carrying at walmart, with the best I've seen being a massively obese man using a mobility scooter, with his similarly massive gunbelt and holster resting in the little shopping basket on the front.