... not certainly mentioned in a file, but my grandfather worked as a mechanic in a submarine-base. He once told me, that from 1943 on they still had some rules about the colour schemes, but they don`t had the paint. So they mixed together what they had, trying to match up the colour. The top grey was, depending on the area where the sub was working in, either middle dark grey (for northern approaches) or a bit a lighter grey for southern approaches. At the beginning of the war, the colour underneath the waterline was a green, later it changed to dark grey.
This means, that anything which can be called "Middle-grey" or "Dark grey" is fine, as there had been changes from time to time. And after one week in service, it all started to become rusty anyway.
Hope that was out of any help,
Jörg
