I recommend you phone the Colorado Department of Wildlife or Department of Fish and Game -- whatever the name of the state department is. They should be able to tell you what areas are open for public hunting. You need to match the hunting season you plan to hunt to the altitude you hunt at. In early rifle seasons, elk are high on the mountain; in late rifle seasons, the elk are driven down lower on the mountain by snows. Ask the folks at the Colorado Department of Fish and Game about research resources you can look into to find what are good areas to hunt: good numbers of elk, appropriate ratios of bulls to cows. There is some sort of big game CD that you can buy that provides good information. Ask questions of locals. It takes some effort to sniff out the information, but be diligent and you will get there.