I live and elk hunt in Idaho every year and Colorado is probably quite similar. Make sure you have good lightweight, waterproof boots and that they are broke in, with you carrying the weight you will be packing on your back. An extra trade out pair of boots for cold weather is advisable. I always have some wool clothing top and bottom and poly-prop undergarmets. The weather can really change so layering is your best bet and bring lightweight gortex rain gear for inclimate weather. Camo patterns for timber and sagebrush mix should be considered and I mix them up. I agree with some lightweight clothing, otherwise you will heat up on the warm days, just be prepared for those Fall storms that can hit and hit hard. Bring several types of headgear for warm days and in-climate, cold and stormy weather. A lot depends on how you are going to access your area and have the ability to pack in the amount of gear you bring. I'd rather have it and not need it, than need it and not have it, but pack in conditions, may limit what you can bring. Best of luck to you.