Note the dull shade of deep yellow on the biplane (it is not a reddish orange) and the slight bronzing effect where the black engine panels behind the cowling have been affected by heat. A convincing detail.
The Ki-55 'Ida' in the background is depicted as grey and the grey does appear similar in appearance to the greys seen in a colour photograph of an 'Ida' airfield line-up. It is a neutral, slightly dove grey. Ki-36 aircraft taken over by Indonesian forces were described in notes made by a British eyewitness at the time as being painted light blue-grey with a dark green mottled camouflage.
For comparison purposes the colour swatches show, from left to right, JAAF paint standard # 14 Ki iro (yellow colour), February 1945 Joint Army-Navy paint standard 4-1 and Thorpe Army colour A17 'Deep Yellow'. Beneath each chip is shown the closest FS 595b match with the DE2000 difference calculation (2.0 or less = a close match).
Thanks to Ken Glass for sharing this image.