As eni fule kno,,,yellow+blue =green.....It's a bit more complex than that, but anybody who has looked at vehicles, buildings,aircraft and boats must have noticed that all paint fades and certain colours are more prone to fade than others.....yellow, fades quite rapidly and needs a lot of solid white to block it's translucency...Red, bleeds through almost anything usually needs a coat of black to "block" it- fades to chalky orange....blue ..will often cast a purplish haze on the surface as it fades.....green....see start
these are generalisations and modern paints are more colourfast but as Parabellum said, Clean air at Altitude= strong UV add strong winds, sandblasting effect of snow/ice crystals plus several years of heat/cool cycling whilst exposed to the other factors and you're asking a hell of a lot from a fresh repaint, let alone one that had probably done a good bit before it was crashed.