What sort of a hunt is it? Horse pack in? At a ranch? Lots of time on foot? Time on foot and horseback? Finding a hide and sitting still for long periods? Thick timber that breaks the wind or exposed sage flats or grassy ridges?
Late October can get pretty cold in these parts. At other times it can be mild. Being prepared with layers and for snow will be wise. The comment about warmest boots leads me to recommend pack boots with removable liners that can be dried nightly or have a spare to swap out every other day might be a good idea to have along. But a lot of time in the saddle and needing to get out of stirrups may have some influence on boot toes or bottoms -- unless your outfitter thinks about that and uses oversized stirrups for winter boots. Take regular hiking or hunting boots as well, in case it is mild or warmish. Something to swap out with is never a bad plan as the weather may swap out over your hunt. And new boots may eat feet.
Midweight Smatrwool merino as a base layer would be good. If wool "is too itchy" a light silk next to the skin then the wool on that would be a warm combination, but still breathable and not over-hot when working hard. Sometimes 2 layers of wool are not too much, depending on the temperature. Had some polypro once. Gotta be careful not to get that too close to a stove to dry it. It melts.
