Been through everything Ki.84sy that I have Andy.....nada. Same for all the JAAF colour and marking books. A shame the link in Aviation of Japan is dead. Typed in Brian Weidemann's name and nothing. As it says on the website, "Very usefully the reference photos are included in the set which will allow modellers to interpret the schemes themselves if they wish to do so". What I see is the grey-green colour that was used on some control surfaces. Best WAG I can do
Shinpachi
Thank-you kind sir. The colour in the b&w pic looks quite light but it may be heavily weathered. It's interesting that the tail is much darker.
Looks like there is a joint in the fuselage behind the pit but that's not where the colour transition is. The structure appears to be monocoque behind that joint so my take is that the darker tail is not because of a cobbled part. Excerpt from Aerodetail Number 24