Yeah Black 6 is tough one, due primarily to the elusiveness of the supposed 'pre-destruction' colour photo - or any pre-destruction photo! (one would think with all the effort going into D-9 research and the facination surrounding the Ta152 tails, that this image, used on the cover of a publication of all things, has not re-surfaced!)
But to look at things from a Block point of view - a basis of RLM81/82 is a good start on the fuselage. I would likely do the power egg in RLM76/RLM83, then lightly blend the colours over with RLM84* an RLM81/82 (as you may note, Crandall depicts the nose green a darker shade than the green on the rear fuselage). Fin I would do the same with (RLM76 with RLM84* overspray) and the rudder would be a lighter shade of RLM76. 5006xx series aircraft didnt sport much in the way of mottling, so that should make life easier...
There is nothing to say the wing upper surfaces need to be only two colours - there are a number of examples of the use of three colours on the uppers (such as II./JG2 - Yellow 11) and any number of reasons for this; repair/maintenance, field application of additional camo... There are also other reasons too, such as fluids/exhausts staining things and soaking into paints (can radically change colours in fact, especially on B&W films). Now knowing this, and the fact that the Junker's supplied egg was probably in RLM76/RLM83, I find it quite possible that a wing set in RLM75/83 or RLM74/75 or RLM82/83, had some extra RLM81 to the wing roots in order to blend things a little - we all seem to agree that colours were oversprayed to create blendings on the noses of the numerous a/c, so why not the wings too?
Remember, the wing sets were supplied as complete 'wings', attached to the fuselage, then the MANUFACTURER would attach bare metal fairings between the wings and fuselage (we see a number of these LATE in the war barely or not painted at all), so it stands to reason that this upper-surface bare-metal would be painted; and logic would say at the same time as the centre fuselage. So if you're flinging round RLM81 on the fuselage, why not on the wing roots too? So I agree with Wayne that RLM81 was a likely colour to blend things together...
The issue now is, WHICH RLM81??? The earlier 'green' version or the later 'chocolate/earth' version? Or the middle 'brown-drab-green' variant???
Dan