I was goofing around with the idea of actually getting back into Fanfiction again and started generating concepts for how all the characters in a HYPOTHETICAL Scepter of Darkness Remake could look...
One of my goals was to make it as lore accurate as possible. As such, if I was going to include any OC's, they also had to be lore accurate.
Kasuto absolutely was not, and as for Relm... well, with the way this story would be rewritten (Princess Zelda being THE ORIGINAL OOT Zelda this time), the only way Relm could actually exist here is if she was a Sheikah, so we have white haired Relm.
The Sheikah in general seem to be inspired by ninjas and Japanese culture, so I think its fitting that in the past they wore something more akin to kimonos. We don't see any Sheikah except Impa or "Sheik" anyway.
Naturally, Relm still is associated with the color red to keep that distinction intact. The basic idea is Relm and Kasuto are Impa's daughters, not just Kasuto this time.