Hi Arno!
Nice to have a fellow countryman on the forum!
You will find all the information you are looking for in this thread, incl. some interesting thoughts about "original" colours:
http://www.a7a10.net/forum/index.php/topic,2322.0.htmlBtw, the 1950 colour is called "Polychromatic Beige" (I think it must be the same for 1951), but that colour scheme was optional. So it was either that, or black. You are free to choose whatever you like best.
If you need anything, write me a personal message, I think I'm not too far away (Bezirk Neunkirchen, NÖ).
By now I dare to say that I know a thing or two about these bikes, so feel free to ask.
Viele Grüße, Markus