Taking this in a different direction, I’m interested in what George’s idea was for the uniform of a Jedi Knight. During ROTJ scripting, he discussed how Knights and masters were not in fact different levels of Jedi but rather were different kinds of Jedi entirely. Yoda was always a guru, Obi-wan was always a warrior. To that end, Luke is seen throughout ROTJ wearing what I assume is the uniform of a Jedi Knight, in various levels of undress:
Perhaps there was thematic significance with Luke slowly shedding this Jedi uniform, as if the defense of his Jedi training was slowly stripped away to reveal the man beneath, for good or ill.
This being the ancient Jedi uniform, one could conjecture about why it is so militaristic and dark compared to the robes of Obi-wan and Yoda. It seems to me that GL’s idea of the Jedi Knight circa 1983 was that a Knight was very much a military position within the Republic, and perhaps the uniforms were dark so as to lend an air of mystery and invisibility to them. To me, the costume is more like the common conception of a Ninja rather than the common conception of samurai clad in kimono, and it is a severe break from Obi-wan’s and Yoda’s attire. If Obi-wan was a samurai serving the Republic, then Luke is a Jedi-for-hire, with no master save himself. It’s interesting that only after abandoning violence does his costume reveal a color other than black.