From what I've heard and read that is just a rumor. The cosmoline will not actually colour the bayonet. It is a form of gold plating from the 50's. Similar to the gold plating found on the slings. Not all SKS's received the plating, but some did. Mine appears to be unremoveable. I've talked to other SKS owners with gold plated bayonets, and they couldn't remove the gold even with elbow grease and a solvent. I would assume if it were cosmoline causing the colouring it would/should be able to come off fairly easily.