Ahoy Madwolf,
The only 2 boats that have similar patterns, but not totally exact, that I have seen
in photos are U-136 and U-334. Very hard to confirm because the angles of the
photos are completely different.
As far as colors, I would be inclined on light and dark greys. I have not come
across any reference which mentions black for camo.
I will keep looking as I have many books to go through.
Hope this helps,
Later,
Joe