Bear in mind that many of these are incorrect for WWII.
Peru, Brazil (incorrect), Turkey (finflash; fuselage and wing was red square with white border), Yugoslavia (until 1941), unidentified (the colours suggest Latvia but the design is incorrect)
USSR (incorrect - LH design), Belgium (until 1940), Finland (Allied forces from 1944), UK (until 1942, thereafter white and yellow rings were much thinner), Spain (Nationalist forces until 1939, finflash - cross on fuselage and wings was of a different design)
Spain (Republican forces until 1936), Australia (from 1956), New Zealand (from 1970), Canada (from 1947), Bulgaria (correct until 1941)
France, Germany (incorrect - LH design, i.e. the brown background), USA (until 1941), Netherlands (before and after WWII but not during), unidentified (possibly meant to be Greece?)
Italy (Allied forces from 1944), Japan (naval flag, not correct for roundel), unidentified (possibly meant to represent Poland, but never used on aircraft, Romania (until 1941, then Allied forces from 1944), Hungary Axis (1942-45, should be in a square)
I’ve been toying with the idea of producing some WWII flags, banners, control markers and so forth, but what would people use?
Would there be any interest in flag or roundel printouts to use on custom boards, or for making “Army group” flags to represent large stacks of pieces?
See the link below to my map for correct insignia for 1942
P.S. I find the suggestion elsewhere on that page that we colour-blind persons are “less intelligent” highly offensive.