I found a rather good site on U-boats that really gets into the paint colors. The thing I came across was that while they didn't use a ton of different colors, the DKM varied their camouflage colors almost as much as the Luftwaffe and Army. Modelmaster does now make most of the various colors they used though.
You will likely have better luck tracking down what colors were on a particular ship at a particular time vice trying to find a standard scheme.
Groot