as a starting point, with their Colorado pdf
, I couldn't find anything restricting open carry for hunting, so long as the person in possession was over 18 and not prohibited from possessing firearms.
I looked through several statutes and didn't see anything, but it may be worth checking a few more of the statutes referenced in that pdf ...and any statutes that are referenced within those
statutes. (It's a vicious, circular spider web of cross-references, but it's usually easy to make a quick judgment on whether the statute matters for what you're investigating.)
As other posters stated.... it's never a bad idea to make a few phone calls.