Dave
I have scoured all my resources on the E.V/D.VII and Osterkamp and have found nothing that confirms this "bumblebee" scheme was ever pictured or mentioned by anyone except in words by Osterkamp, himself.
This scheme seems to have been perpetuated by model companies, authors, illustrators and artists for a long time, but no one has ever referenced a photograph, to my knowledge.
Still, it is most attractive and not improbable. It makes a good speculative scheme.
Cheers
Syd