well if i was doing a film project at red rocks i would try to start in the morning. at least before noon. the yoohoo video we shot there last feb. was filmed at like 8-11 in the morning and keeping in mind that our camera wasnt that great, the light turned out amazing on video!
by the way, the forecast is mainly sunny, high of 60, some clouds from time to time, and winds of 15-25 mph. the wind will be a little annoying but shouldnt affect anything other than camera interviews if you were planning on anything like that.
but in the end, its your project, so you make the calls.