I can't weigh in on hunting Colorado but I can definitely say that in Idaho and Oregon moon phases are becoming a very determining factor on activity before and during the rut. My thought is it is mostly hunting pressure that is making the elk very active at night with any kind of moon. In the last few years I've camped in several basins that have lots of elk and do get some pressure. I can listen to them bugle and run around all night but then 1/2 to an hour before shooting light its like a light switch turned off. With a moon and at peak rut, mid-day can be excellent. 3 of 6 bulls I've harvested in the last 7 years has been at noon, even when hot. Anymore, I can predict what hunting the rut is like by looking at the moon phases and I plan accordingly. The 2nd half of September the year is looking good for active animals during shooting light.