git log --graph --color inconsistency

Hello,

I use git version 1.9.1 . With

  git clone git://github.com/pocoproject/poco.git
  cd poco
  git log --graph --color=always

and scrolling a bit, I see http://mail.aegee.org/dpa/git-log-graph-color/git-log-graph-color.png .
My expectation is, that one branch keeps its color consistent in "log
--graph", but here it changes from red to green without any obvious reason.

Any ideas?

Greetings
Dilyan