This post contains spoilers for The Acolyte finale. Lightsabers don't automatically turn red when one turns to the dark side. Anakin never bled his kyber crystal in the prequels, explaining why ...

Revenge of the Sith, Palpatine wasn't always supposed to wield a red lightsaber, instead it was nearly a different color.

As part of the May the 4th merchandise, Disney has revealed the return of the Anakin Skywalker and The Ren Legacy Lightsaber Hilts.