I beleive that Cyanide colors are not as durable (generally speaking) as bone charcoal. But, specifics of the process and the type of steel can influence this i am sure.
Not arguing with your experience, but, mine is the exact opposite on Darne shotguns. I have handled few (none, truth be known) from the pre war era of bone pack hardening that retain a lot of color. The cyanide finished guns that came post war are often in great shape:
This photo doesn't actually do justice to how rich the colors are on this example. Late 1940s vintage R10 20 gauge.
I wouldn't want to see cyanide case colors on a big three English gun. But, I wouldn't want to see St. Ledger colors on a post war Darne, either.
Some guns look perfect with cyanide. Some, don't.
Best,
Ted
