i mean, the out-of-universe reason for dark robes is obviously foreshadowing, but the in-universe reason's probably close to that imo... considering the humble jedi robes might remind him of his & shmi's shabby slave robes, he could prefer darker colours to distance himself from his past. (the "i hate sand" line was basically about how much he hated tatooine, just said awkwardly). also, dark robes don't show grease stains as much from his mechanical tinkering (or other things like dirt/blood) :D
honestly this is 110% valid. the beige jedi robes being a reminder about his former life on tatooine? the darker jedi robes better at hiding grease stains because of his love for mechanics?? this is ridiculous on point and I LOVE IT















