There are 110 year old A Grade Fox shotguns that have the most brilliant well preserved case colors any of us have seen. I don't think they were protected from light. I also don't think my 145 year old Westley Richards eight has been specially protected from light, but it is still new. The hidden exterior parts of many double guns have been protected from wear and are "new", but they weren't particularly protected from light. What is the explanation? Light fades case color or light doesn't fade case color?