HAH!I just had a long and frustrating thread about this.
As far as I was able to find out, that strip at the left is it. To make all Audio red, MIDI blue, etc, you can use Ctrl to select the desired multi tracks, hols down Ctrl while clicking that left strip on one of the selected tracks. This will change all selected tracks at once.
What i does _not_ do is make that the norm for every project. Even making a template will mean that you still have to fix any new tracks in your next project