him-e:

Anakin didn’t turn to the dark side overnight. It was a progress. The seed of darkness had always been a part of him, and the more he chafed under the jedi doctrine and ideology, the stronger that darkness got. The black-clad Anakin we see at the beginning of RotS is a person who’s already tapped into the dark side and been on the brink of falling to it, long before Order 66 and the padawan massacre.

Star Wars isn’t exactly subtle with the visuals—the protagonist’s increasingly darker robes are supposed to reflect and symbolize the slow but steady rise of the Dark Side (in Anakin) or a progress from juvenile, naive “innocence” to a more mature and complex personality and sense of morality (in Luke, whose clothes also get darker throughout the story, to show a) his personal growth; b) his increasing familiarity with the Force, which is… not necessarily the good and pure positive energy that we might be tempted to believe, but a mysterious, powerful, sometimes dangerous and uncontrollable eldritch entity; c) his beginning to question Yoda’s and Obi Wan’s rather black and white morality; d) his getting to terms with being his father’s son and seeing him as not as irredeemable as his mentors thought. He wears full black in RotJ when he’s made up his mind about trying to reach out to Vader instead of killing him. To get there, Luke had to face his own darkness—and similarities with Vader—and eventually reject it, but not before having properly confronted and experienced it.) 

(tbh I fully expect Rey’s clothing to go through a similar “white ➡ dark” process, even if she isn’t tempted by the Dark Side. In fact, by the end of TFA, she’s already lost her *virginal white* desert garments and started wearing grey. Subtle.)