Erich - you prefer the EE take over Japo??? I must admit, I have sort of leant the other way myself...
My main problem with the EE take on 500408 comes back to the wings - I dont see why the Germans would be using a 'third' colour, when they were actively trying to rationalise on materials, complexity, work hours, etc... Thus, my interpretation of RLM83 under the wings (assuming the top colours were in fact RLM76 and RLM83). Of course if we choose to look at the Grey on the wings differently, things change; I shall explain my thoughts.
Those German late war pigments seem to be REALLY unstable or sensitive to UV light/weathering. If 500408 was given a set of wings that had been painted RLM75/RLM83 (which is far more common), with the RLM75 being from a 'contaminated batch' that just weathered within weeks of being exposed to the elements (ie, really 'chalky', like Im sure we've all seen when we have screwed up paint/thinner ratio's), then it is quite plausible that we could see RLM75 lowers, with RLM83 and FADED RLM75 uppers. Additional to not being directly exposed to the sun, the continued 'conditioning' of the lower surface RLM75 would help maintain the colour, with oil, moisture, gun gases, etc, 'soaking' into the porous/chalky finish.
Still, in my case (and as I've said elsewhere) I tend to be more about 'tonal difference' on the finished model - if the colours display something approximating the appropriate tonal difference, anyone with have a VERY hard time arguing with your solution!
And this one of the really cool things about D-9 modelling, the camo and the hours of frustration and revisions and 'forehead-palming' you end up doing! My solution for my D-9 211164 Black <4 does not correspond to ANY other solution I have yet seen (Japo, EE, Aeromaster, Eduard, Superscale) - for example, I am SURE I can see a W3 lower wing surface; Im sure the tail is mottled with RLM81; Im sure the 'repair light grey' is the same colour used under the rumpfband overspray, on the fin LHS, under the LHS Balkenkruez and the LHS wing root; and I am pretty sure I can see traces if RLM82 where both Japo and EE say it isn't!
Fun, isnt it!
BTW Erich - you were working on your own D-9/Ta 152 work, were you not? Is that still happening and is it near or far?
Dan