The question of natural metal finish (nmf) under surfaces on some Pearl Harbor 'Kates' has run long and in its 1/48 scale kits Hasegawa has variously depicted grey green or 'silver'. The late Jim Lansdale was of the opinion that the finish varied as the result of production chronology and that he had examined KanKo artefacts where the dark green was painted over nmf and others where it was painted over the 'olive grey' finish. He estimated that the last 200-300 KanKo produced by Nakajima up to August 1941 were probably in a factory applied overall olive grey scheme, implying that older aircraft already in service may have been camouflaged dark green on upper surfaces but retained nmf under surfaces. His extant sample of metal from the so-called 'Hospital Kate' did not have any primer and he had seen no evidence of any primer on the olive grey painted aircraft. Does that imply that they were possibly IJN Depot rather than factory painted after the olive grey paint was adopted for the Zero? In any event the olive grey appears to have been the warmer. more yellowish Nakajima colour. It was possibly patches of that paint showing through the dark green camouflage paint that gave rise to the idea of PH KanKo sporting 'brown' blotches on the green camouflage.
A fabric sample from the 'Southeast Loch Kanko' had a layer of red oxide, a layer of aluminium and a top coating of olive grey. A piece of the rudder fabric had bright red over the olive grey layer. He noted that according to Bob Mikesh the under surface fabric of a B5N amongst the approximate 50 manufactured by No. 11 Kokusho during 1939-40 was doped a blue-grey approximating Munsell 5 PB 6/1. That would be approximate to FS 36320 so possibly J3. But in addition to the manufactured aircraft the No.11 Kokusho may have reconditioned or modified many B5N airframes from 1942 until March 1944. The B5N was also manufactured by Aichi from June 1942 to September 1943 with a run of approximately 200.
The heading photo is from film footage of a Midway-era KanKo taking off and the lighter outer wings are intriguing. Is the lighter colour on this bird olive grey (or 'grey poupon'!) and was the darker green (?) camouflage applied on board the carrier with the wings folded?
Make of it what you will . . .
Image credit: B5N photo web; Colour schematic © 2024 Aviation of Japan