As I recall, when the Developers and Judges ranks first came out we had pretty much every Admin, mod, and dev (except for senku for a while) to be a judge. I believe the reason why Senku wasn't was because he still made addons that needed to be judged, and it would be a conflict of interest or something like that. I think the rank was made so that devs that were judges could have moderator privileges over certain forums. At the time, I don't think we had anyone that was just a judge.
I think the main reason that both ranks are orange is that that color was meant to mean part of the staff, and not having to do with moderating the forums. Devs, staff, and judges have the same privileges over most of the non-private forums.