I think what Dean was mentioning is decks of destroyers not over accommodation, such as over the Boiler room, where burnished with something like what was used on coal fires, which gave a dark greyish steel colour as were some gundecks on raised mountings. The area over boilers has a name which slips my memory for now, but paint then was expensive and destroyers where cheap warships compared to cruisers etc. Also Home Fleet Destroyers between the wars were painted what was called North Sea Green, which was medium grey but based on green rather than the blue based medium grey of major Home Fleet units. I do have a model destroyer built between the wars by Chatham Dyd apprentices and presented to a Destroyer Captain who kept in his cabin until the vessel was scrapped after the war and she was painted in the original North Sea Green.