Lots of options. IMO rain gear falls into two buckets. (1) the kind you bring when you know you are going to get rained on and may end up living in it like in Alaska or the PNW. (2) the kind you bring just in case.
For back East, I am usually in the just in case category. I mixed and match a set of Sitka cloudburst, a storm front jacket, a set of kuiu pants and some packable Patagonia lightweight stuff. I also have a tarp called a gatewood cape that doubles as a poncho. Depending on the weather, I have more or less of those with me. I hunted 3 days straight in the cloudburst in 35-40* rain and was quite warm and dry. The packable stuff is nice piece of mind just in case but would get shredded with hard use. The poncho is fine for a passing storm and as an emergency shelter but you can’t bow hunt in it and high wind whips it around.
It is great to have the heavier stuff for big Rain but if I am being honest, for me in NY and PA, the lightweight stuff goes into the field more. Cabelas has a set that was fairly cheap and seems to be well reviewed.
FrogToggs are good for Option #2 from DeskJockey's post. There cheap, light weight and packable. Good to have if needed...not for an Alaska hunt though!
Any lightweight, breathable raingear will let you down. I've had brand-new top of the line stuff out in Alaska and 8 hours into it, it's saturated and there is no coming back. I've gotten hypothermic twice because of it and was luckily able to get to my tent and shiver it off before things got worse.
Rubber is the only thing that will keep water off of you but you'll sweat it out if you're moving. Breathable stuff works for a bit but I don't trust my life with it.
Hmmm. I don’t think I would choose rubber for a September, Colorado mule deer hunt. Depending on my other layers I would be looking for a light breathable top and bottom. Cloudburst from sitka is a good option. If I was wearing a soft shell that could shed a little water, I would go with something even more packable to go over it in the event of a real downpour. That is how I use my really light packable stuff. Basically just a final waterproof outer layer for heavy rain.
I didn't pay attention to the Colorado part. Breathables should be fine for mountain west since y'all don't get deluged like the East, Northwest, or Alaska.