The color scheme depends on when your boat was built ,were it was stationed ( the Med. etc. ) where it was maintained etc,etc,etc. pre-war boats were red bottom ,grey top with a black belt at the water line. Most war year boats were dark grey bottom with light grey vertical sides and dark gray horizontal surfaces. When in the med. there were several camoflage paint schemes used. Also many early war boats wood decks and these were dark brown in color where later steel decks were dark grey. U-boat commander SCHNEE painted his conning tower of his type XXI white because he felt that a ligther color was harder to see from the air. So , as you can see there was alot of variations that depended on time frame of the war etc. Also as the war went on boats were painted with anything that was on hand to get the boat ready for a war patrol, or to free up a building slip.