When I did the wooden/plastic model of this, I wrote to the Kreigsmarine museum and got some great info on colours. The anti slip paint on the outer deck was either a black or a very dark red/burgundy colour dependant on where they got repainted when they got back to port. I used German navy grey for one of the colours, I can't remember the other colour now. Hope that helps a little.
@JohnsModelmaking I enjoyed the build. The hull was plastic front bow and stern and the rest of the hull was wooden planking. There was a couple of cut out areas for engine room and command deck. I did mine weathered to show it had come back from tour. A lot of the paint would have been washed off due to the seas, so my sail (coning tower) was very battered looking.
I just wish I had some of the pictures and reference details I got from the Kreigsmarine museum that I could have sent you to help you out, but once I completed the build, I threw it out.