James F Lansdale has now posted some Munsell values for browns in his own report on IJN "kumogata" (cloud pattern) camouflage at j-aircraft.com
These values for H2 are drawn from the Yokosuka Ku (Yokoku) report No.0266 and differ in appearance by researcher as shown. The colours are much less reddish than the facsimile Kariki 117 chip for H2 and reflect Watanabe-san's reservations as expressed in Arawasi magazine:
"Seeing these colours, grave doubts remain as the differences are so great, even taking into account colour shift and fading.
In that case, could there also be the possibility that the colour number used in Kugihô 0266 were according to a paint specification other than (Kariki) 117? We presumed that the colour numbers used in Kugihô 0266 were those in (Kariki) 117, but there is not one reference to (Kariki) 117 in Kugihô 0266."
The colour measured from the remains of a Type 1 Rikko (either K-913 or K-393) by Dr Charles Darby appears to be much closer in character to the facsimile chip for H2 and the Navy colour N11 as identified by Donald W Thorpe, but of course we have no way of knowing whether this colour was actually H2 as applied.
Also, it is not possible to determine that the brown colours as displayed in Kugihô 0266 and Kariki 117 were the same brown colours used in the early kumogata schemes applied in China, as depicted in the contemporary artwork shown here. The precise appearance of the early kumogata browns remains somewhat elusive.
The Hasegawa suggested GSI Creos paint mix for their G3M kit results in a rich, reddish medium brown somewhere between 5 YR 3/3 and 5 YR 4/4, a colour closest to Thorpe's N11 Medium Brown (5 YR 3/4) and the colour found on the Type 1 Rikko K-913/K-393 but with a stronger chroma.
Not all bad news for modellers, though. Armed with the contemporaneous artwork and the colours identified in Kariki 117, by Don Thorpe and shown here, it is possible to make an informed choice about how to present the IJN browns on a model.
Images credit: Rendered colour chips ©Straggler