When completing my 32nd Parallel VIIc, I used a flat gray enamel on the upper hull that has shown no ill effects from water. This was specified as 'gull gray', for use on late model US Navy aircraft. The lower hull was painted flat black entirely, though I'm contemplating the red paint that's more correct while the boat is going through a major yard overhaul. OTOH, photos of both U505 and U995 don't show a red lower hull, or are their paint schemes correct?

One of the great hinderances in painting a model is the scarcity of color photos of uboats.