Couple of years ago my sons and I were going through CO, and went through both Boulder and Ft. Collins (CSU). Boulder speaks for itself, but I was impressed with Ft. Collins as a college town. The campus is very nice as well.
In Denver, those folks be driving down one of the main thoroughfares...see a piece of litter...pull over and pick it up and put it in they vehicle...no ****. really..have seen it.