In the USA you definitely won't be able to sell it outside of your own state - the Endangered Species Act prevents sales or commercial use of any items made from such animals.
Whether you can sell it within Colorado, will depend on on local state law on endangered species. I believe there are some states that will allow local sales if it's older than a certain age, but I don't know which states, or what proof of age or permits you might need. Many states won't allow it at all. Try googling colorado endangered species law, or contact your local wildlife office.
It might be simpler to give it away. There is a USA charity that uses old fur coats for rehabilitating animals - someone else here may give the name, I can't remember. If you give it to someone to wear, they should be made aware that they can't sell it or make any commercial use of it, and they would need a permit to travel outside the USA with it.
These kind of items are governed by strict laws all over the world to prevent the illegal trade in endangered species. Just occasionally exceptions are made for older items, but even this is strictly controlled, and in most cases selling them is not an option.