A lot depends on how you are wanting to hunt.
Are you gonna truck camp, where you can bring nearly all you want to, or are you backpacking in ? Are you backpacking in a mile, or way back in there ?
Do you want to go chase them or find spots and stand hunt ?
Definately get some decent boots, worn in to your feet. Where I go, you will be doing a bunch of up and down hill walking. That puts different strains on your feet than street or stairs walking. Makes for blisters.
For Colorado, I have gone thru a lot of changes, but I have gone away from Bean boots (my foot move around too much in them on the slopes), from heavy soled, vibram and the like boots (these feel great, but they tend to be a bit noisy and they get HOT).
I now kinda like a classic hiker with softer, less aggressive soles. I wear two socks, first a lightweight silk stocking, then a medium weight wool sock. I have never had a blister form while wearing this combo.
In CO it gets warm during the early season. OK, hot might be a better word. The sun is hot and the nights are not. Cotton shirts and cotton pants work fine for me. I carry a wool shirt or vest in my pack, plus lightweight rain gear. I kinda like ponchos cause I can cover my bow as well. I now use a Bison Gear Lost River pack for my own reasons. I carried out half a boned out cow years ago in a Cabelas day pack (with a game bag inside and extending upwards). That was not the most pleasant time I ever had.
I have had it freeze good at night, but not very often during the first two weeks of season (7,500 - 8,000 ft elevation). It does chill right down after the sun sets though. Have a decent hoodie jacket for camp wear.
Make certain you have a way to obtain water (and drink it. . lots of it). Its important
I like to stop for the night at a kiss n park along the highway just past Denver. That gets you a night at good elevation, to help acclimate. Then give yourself a break the first coupla days hunting.
Others can add.
ChuckC