RAF marine section craft in the Med were not painted white during WW2. This colour scheme came into use under A705 28th August 1947. In wartime, they followed the standard ASR colours. Depending on the year, the decks and superstructure would have been yellow until circa 1943 unless operating on the east coast where they were ordered into the decks and upperworks to be the “the general tone” of the camouflage of the ship. It is about then that they started to paint the superstructures Dark Battleship Grey. Later in the war, the RN introduced a deck colour called B15 for coastal forces and the RAF boats were supposed to use coastal forces deck colours.
BS381C 32 Dark Battleship Grey still exists as BS381C 632 Dark Admiralty Grey.
Post WW2 in 1947, Home and temperate waters including Gibraltar were black hulled, BS381C 632 Light Grey superstructure and BS381C 632 Dark Battleship Grey Non Slip decks. Tropical and sub tropical water including Malta & the Mediterranean used the same deck colour but were otherwise white.
FYI The 1937 orders on colours had the decks as varnished but the superstructure as Dark Battleship Grey.
A WW@ shot of an ASR in the Med attached.