Criminal Law Questions? Ask a Criminal Lawyer.
There have been a few cases nationwide which said that an ANTIQUE black powder gun was exempt from the rule stripping felons of thier firearm rights... but it is not the norm and definately not worth rolling the dice on. There is no case in CO (that I could find) that said a black powder gun, even an antique, is not a firearm. So no, black powder hunting would not be legal.
A bow and arrow looks to be legal though (but not a crossbow!)