The splendid box art for the 1964 Tamiya 1/50th scale Ki-43 III Ko depicting an aircraft of the 48th Sentai over China, is ambiguous in appearing to show a slightly olive green version of ohryoku 7 go shoku with natural metal undersurfaces. The instructions, however, are interesting in that they suggest that the upper surfaces were "brown (just like olive drab)" and that the under surfaces were "The same as that for upper surfaces excepting that it has been lightened with white." This description exactly conforms to the recollections of Mr Shimoune.
Although the study is ongoing the following paint colours have been identified as being applied to JAAF drop tanks:-
1. An unidentified neutral grey - for which the closest FS value is 36293 @ 2.13 (it is slightly too blue). This appears to be the colour of the drop tanks on the aircraft in the colour photograph posted below.
2. A pale blue-green, JAAF paint standard # 17 'Tan Sei Shoku' - for which the closest FS value is 25352 @ 2.25, a good match.
3. The yellowish green colour # 29 'Ki midori iro' - for which the closest FS value is 34151 @ 2.15, not quite yellow enough. This colour was also used for cockpit interiors.
4. The olive drab #7 'Ohryoku nana-go shoku' - also used for top surface camouflage and interiors, the approximate FS equivalents to which are 33070/34088. The swatch included above is gradiated from left to right to show the brown to green ends of the colour range for this paint.
5. Yellow - which is presumed to be the standard orange yellow in use for IFF strips and trainers (q.v. Army Trainers) although a Ki-84 Hayate tank is cited to be in a yellow colour of approx FS 33655 to 33538.
Image credits: Box art & instruction sheet © Tamiya 1964; Rendered colour swatches © Straggler 2009