[Sergio Luis dos Santos]

Even before WWII I can remember other uses of yellow for better vision. Just remember the Dornier and Blohm und Voss planes in the Trans Oceanic Flights of Lufthansa from Africa to Brasil. Upperwing surfaces (From photos it looks horizontal stabilizers uppersurfaces also) were in bright yellow for safety. Easy to spot on water surface from above. Clear colors were of use years before on sailplanes. They use to land in any place when winds stops! Even the record-breaker He-115 had large areas in yellow.

Didn´t Italians have an "Africa" scheme, ivory with red strips on their planes and some sailplanes too? Surely for better identification in an emergency landing on sea or sand.

I also think several planes on 20´s and 30´s doing long distance flights over water or forests also have light colors on uppersurfaces but have nothing with me, just a guess.

So we can verify that years before WW II some colors were recognized as being easily seen from distance, like the yellow.