When I was a teenager my family moved from LA to Denver. There were some very distinct differences. For one thing we all really missed the ocean. The mountains are wonderful but I was a real water baby and I had a hard time making that transition from surfer to skier. Also, it is quite a change to go from big city living (like in LA) to a smaller city like Denver. Although Denver has come a long way since my folks moved us there 20 years ago, it still has a small town sort of feel to it and can seem a little less sophisticated than LA. If you are planning to move to an even smaller community, really investigate it. I have seen the isolation really take its toll on former city folks when they move to the mountains. An other thing to keep in mind is the weather. The winters are cold! and snow storms can keep you trapped inside for days at a time. I know this really bothers my mom (who has lived in Co. for over 20 years). The winters can be very barren and gray. Snow that is beautiful the day after a storm is very depressing when it is filthy on the side of the road weeks later. Trees have no leaves (except the pines) and there are no flowers for months. This lack of color for months on end can be very disheartening to the Southern Californian who is used to green and blooming flowers all year round.
The air quality, while better than LA, is not great. There is a lot of carbon monoxide trapped by the mountains in Denver. But the skies are clear and, as an earlier poster mentioned, impressively beautiful. Allergy problems are at a minimum due to cold winters and a dry climate (bring your lotion). By and large, it is a very healthy, active, get out in the great outdoors kind of state. People are generally very friendly and there is a lot to do.
As far as racism is concerned, I don't think you have much to worry about. The Denver metro area (Boulder and Colorado Springs too) are ethnically diverse and have not experienced much trouble in that area. I live in Texas now and the race issues are much more pronounced in the south than in the western states. I don't remember there being much of a problem.
While I don't live there anymore, my parents still do and I visit Denver about 3 times a year. All in all, I really like it there but it was definitely a challenging transition from LA to Denver. If you need more information, feel free to send me a message with more specific questions and I'll see what I can do for you.