Really interesting.
Like you Orell - I can certainly see this being a bigger thing for the Padawans (I think that's what you were saying about children at the end) and Apprentices - a way of identifying one's self that break from the "allowed robe norm". The braids more than just robes with slashes of color (at least for those species with hair), simply because it would be a way for them to age appropriately individuate from their "family". For those without hair, then I see both creating fake braids to fit in/but not as well as then using slashes of color in robes/robe color. Depending on how lenient their Master was of course.
But then as one grows into adulthood, and is more secure in their own identity (or maybe...), grows out of such displays of rebellion.
Would be a fun thing just to play with anyway, among a guild or just among some friends - or your own personal back-story for your Jedi and where they came from. (Doesn't have to be jedi...)
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Now Noth as to your final question - if color/clothing choices plays a roll in your RP.
Not for a Jedi no, but for Karmic - it means so many, many things.
One of the core concepts of Karmic's character centers around (duh) manipulation, and in particular for her - the use of subtle (assassin so again duh..) techniques in order to do so. But as she was a slave and is now a Darth - such strong training means that its gone beyond just the "Job", obviously, into who she is as a Personality/Person. I like to joke that almost everything about Karmic, including most of the words that come from her mouth in public, have multiple meanings. As much as I'm kidding (because I don't think about what she says THAT hard...lol), I'm not kidding with how she definitely uses clothing and colors as part of her personal toolbox - to manipulate others without them realizing it.
She always has on (icily and oocily if you inspect her) her hand and wrist slave chains. I quest with those suckers, I Rp in them, - they are in reality - ALWAYS ON!
I have four tabs of clothing, some in multiple color combinations - because of that reality. At any given moment you are seeing her, what Karmic is wearing and the colors she has chosen to wear all have a purpose and meaning behind the more superficial appearances. Including the reason she never wears pants.
Much like people use the type and color of a flower to send certain messages; Karmic and her chosen clothing work the same.
Its always been more interesting to me - as the person behind the character - the sorts of things people don't ask about and don't figure out (icily or oocily). When I think they'd be great RP conversational topics, and are "more obvious to ask about", but people rarely do - outside of the superficial assumptions most make about what Karmic's wearing in public.