Tony,
As much as I'd love Yellow 20 to be part of a protection flight, the sad truth is that Erg KG(J) purpose was to re-train bomber pilots (from KG6, 30 and 54), via piston engined aircraft (i.e. yellow 20, etc), to fly the Me 262. Once trained they'd be farmed out to one of the KG(J) units.
Yellow 20 was reported (via 1 TAF - thanks to Rabe Anton here:
http://109lair.hobbyvista.com/articl.../ge20/ge20.htm) as a G-4 (typo?) or G-6.
It's markings were also reported as 20+|, although I believe the III. gruppe bar is a misinterpretation of the white trestle stripe under the tailplane. Additionally I have some evidence to support the theory that the fuselage band was not an overpainted yellow one, but was in fact red. I have a little more info on the aircraft of this unit, but it'll have to go PM (I'm afraid) if you're interested,
Hope this helps,
Chris