Discoloration on the receiver.
 

I have a 28 Ga repro that was purchased in 2002 as a used item. I strongly suspect that it is unfired. However I can see light and dark areas on the receiver as though the bluing is bleeding out. Is there any thing that can be done to stop or retard the discoloration.
At the onset I kept the shotgun in the original case. Lately however I've begun storing assembled in the safe and lightly wiped down with an oil cloth. The safe does have humidity control. The shotgun is a DHE "D" grade.

The Repro's are known to have 'not so permanent' "case color", and I put case color in quotation marks because they weren't done in the bone and charcoal method used by the original maker of Parker shotguns. But rather, they were done chemically and are prone to flaking and wearing off quite easily. I can't comment on the possibility of the Repro colors fading as I have no experience in that area.

Relax.

Repro receivers were never blued, they were case-colored, so it is impossible for any bluing to bleeding out. Can you post a couple of good in-focus pics to confirm what probably many of us suspect?