Err, not to act like I know everything or anything, but if it helps at all here's my viewpoint...
The color symbology in the clothing choices actually seem very intentional, and have some subtle depths I think most people miss:
Anakin in TPM: gray tatooine duds, the wears a white padawan outfit very much like Obi Wan's
Anakin isn't entirely all goody-yippee-skippy in episode I if you pay close attention. Look at the way he bites Padme's head off at one moment- "I'm not a slave, I'm a
person." Not much, but you can see some bitterness in him from the way he's lived, and I suspect the dirty grayness of his robes to be symbolic of that.
In AOTC: dark brown leather robes (leather? what other Jedi wears leather??) over slightly lighter, but still dark, brown cloth robes, with beige on the bottom layer.
He's got a big 'tude from the beginning here- you can see quite clearly that he's not pleased with the way he's not "progressing" as much as he'd like. He thinks he's pretty badass, and that shows in the way he handles himself in the movie's first chase scene on. But on some level he means to do good... and in fact is somewhat good. Beige inside robes, then.
In ROTS: just like AOTC, except [/i]the bottom layer is now dark brown.[/i]
He's getting sick of his lot now, and, well, we know how the plot goes here. And notice something else: towards the beginning he wears a brown robe over his outfit, but when he becomes Darth Vader, isn't he wearing a black robe?...
Then of course, the Darth Vader suit is all black. Obvious symbology there.
Luke in ANH: white and brown farmin' tunic. X-wing outfit doesn't count, I think. Then there's his ceremonial outfit; don't know what's up with that yellow jacket, but I spy a black shirt and brown pants, even if they are out of Han's closet (why does everybody raid his wardrobe?).
Luke means to do quite good here, and for the most part isn't too bad. He's just got this anghst about how he's not progressing as much as he'd like, and... wait, this sounds familiar. But he doesn't think he's badass; he just wants adventure, and to be some heroic warrior. Then Obi Wan dies, and Biggs... I'm not sure if this is intentional, but his ceremony garb suggests something a little darker in place, if you think about it- but that's probably more accidental.
ESB: X-wing/Snowspeeder outfit and Rebel snowsuit outfit, sure, but when he wears his own clothes, suddenly he's wearing all medium-browns...
Here we find Luke, still meaning to do good, but he's been around a little more. He's kind of trying to find his bearings and figure out what to do, while protecting those he loves. But he's got some problems... overconfidence, a lot, as we see in his fight with Vader and the way he first confronts Yoda (Jedi training test #1 failed there
). He wants to do good, but he assumes too much of himself...
ROTJ: all black with dark, dark brown tunic (at least it looks brown if you look closely at the skiff scene- bet that's why the POTF2 guys messed up originally
).
Luke has been through a pretty bitter confrontation, learning that someone so horrible as Vader is his father. He's angry... look at the way he acts when Yoda says "unfortunate this is... and unexpected." "Unfortunate that I know the truth?!" he says. Luke is confused, and feels the pull of the dark side as well.
He's more mature and calm- not confident, but calm- and experienced, as well. But he's not doing everything right- was he really
supposed to choke those guards? Maybe push them away... but
choke them? It all really comes into question when he confronts Vader, though- pay close attention to his responses and behavior to what the Emporer tries to do, to what Vader says. He's trying to do the right thing... but on the other hand (haha)... and when Vader threatens Leia after probing Luke's mind, Luke is at first horrified, and then explodes, beating the crap out of Vader. He very nearly kills him- he hears Palpatine goading him, but something feels wrong. He looks at Vader's missing hand... then to his own... and it all clicks. He realizes that he is becoming his father... and he decides not to. He tosses his lightsaber away, and proclaims "You've failed, your higness... I am a Jedi, like my father before me!"
Throughout ROTJ, and in Padme's dying words, you can see that both, in their very different experiences, felt and knew there was good in Vader- that Anakin was still there. But where Anakin made the wrong choice, Luke saw what was wrong, and decided to make a different choice.
Incidentally, Luke also called it perfectly when he told Palpatine that his overconfidence was his weakness
So now that I've had a long sappy speech explaining 75% of the plot, I hope that somehow clarifies something for somebody. >> It makes sense to me, and is in fact perhaps what I love most in the Star Wars story... *
shrugs*
Incidentally, look at Obi Wan's robes, too. At first he's got all white, and he's just sort of lofty and sees everything in a calm, slightly humorous way.... then some time after Qui Gon's death and training Anakin for a while, he starts to wear beige, but it's still light on his bottom tunic layer and pants... and then in Episode III, he adopts a dark, reddish brown bottom layer and pants. And then in the original Trilogy his colors are similar to this. Not turning evil, but becoming troubled and somewhat guilty... darkened, in ways.
And Clone/Stormtrooper armor is another example- white on top, sure, after all, they seemed like they were the Jedi's allies... but then there's black underneath...