Ah yeah, I wasn't sure how literal you were being with the mood ring lightsabers! I can see an actual mood ring lightsaber (and how to make it stop) being a cool plot for a comedy fic, but, uh, not for anything serious. And I the Darksaber is ... well, uh, I have some vague Dark Side post thoughts about how people keep trying to make the Mandalorians the most supremely coolest by giving them Jedi stuff, like a lightsaber, instead of having the ritual item of their leader be a helmet or something else more suitable. So I'm a color purist!

So that "healed Sith crystals are white" thing is from canon? I've seen it in a fic or two, but didn't care enough to go canon-checking.
Just for you, I went and checked Wookieepedia, and it's from the Ahsoka novel! She took an Inquisitor's crystals and healed them, turning them white.