Which collection do you mean ? Mr Witt had actually two B12 5.7 E31, where he sold the blue one to a czech guy. Mr. Messner also has a B12 5.7 E31 in blue.
You can see him here with only a fraction of his collection :
https://www.youtube.com/watch?v=uBqdjseIErg
(It's from swiss tv - so only german and swiss-german)