What I can find on my search on the internet is that a brown/red color can happen in GSD. Some nice pictures and an easy reading about the genetics you can find in the links below.
http://www.bluedogs.8m.com/fawn.html
http://www.bluedogs.8m.com/7week.html
http://www.bluedogs.8m.com/info.htmlhttp://www.bluedogs.8m.com/info.html