As for the Bf 109 K-4 "Gelbe 6", I've put on line a blow-up of this machine:
http://www.flickr.com/photos/2809206...in/photostream
Examining the rear fuselage, I've the conviction there is a light colored RV Band. Unfortunately partially blurred by the overlying clear plastic sheet, it is either a uniform light color, pointing towards 3./JG 3, or a three segmented light color band, pointing then towards either 3./JG 2 or 3./JG 300.
JG 2 can be pretty safely be excluded as it wasn't flying any Bf 109 K-4's. This leaves us with either JG 3 or JG 300. The uniform low tonality of the rear fuselage behind the Balkenkreuz points more towards a JG 3 white RV Band. Having just checked in Prien and Rodeike, only III./JG 3 did fly from 18 December 1944 onwards Bf 109 K-4's. Given the low contrast between yellow and white, there could be a III./Gruppe vertical bar, maybe to be discerned on the original. I would thus cautiously suggest a 11./JG 3 machine, without totally excluding one of the rare Bf 109 K-4's flown between March and April 1945 by III. or IV./JG 300.
Let's hope that the happy deep pocketed buyer of this pic will generously share the details of the rear fuselage;-))
Cheers
Marc