I think Lucas only came up with the official Jedi robes for TPM, actually. Luke's clothing in the OT is a very good development using the meaning of the colours. In ANH he wore white (for youth, purity, unspoiltness), in ESB he wore khaki-brown (symbolic for him aging and learning) and finally in ROTJ he wore black (sign of maturity). So that was indeed excellent. And I am quite sure Luke couldn't get a subscription on Jedi Fashion Monthly anymore.
I actually liked him in black. I remember one of the monthly Star Wars comic books from the eighties that featured a story about Obi-Wan Kenobi as General. He wore black in that story too. I know that's EU and totally useless when it comes down to discussing the movies, but it demonstrated how people thought about Jedi in those days. I really think Lucas did not come up with Jedi and Sith outfits until working on TPM.
queeq out