Hunting in Colorado especially at altitude you need leather or cordura type hunting boots not pac boots. The boots need good support and the best tread you can get. I personally like the Danner series of boots which come in many weights, designs and prices. I normally use a Danner grand slam boot which is an all leather Gor-tex version of the Pronghorn in 400 grams of thinsulite. I wear one pair of smart wool medium weight socks and have never been cold or too hot. Most of my hunts have been 2nd season rifle and often has been in snow. Good well broken in boots are probably one of the most important items of gear needed for elk hunting.