According to the Disney canon, Kyber crystals are inherently resistant to the dark side of the Force, and dark siders must bend them to their will for them to work in their lightsabers, creating a bleeding effect which is why all dark siders have red lightsabers.

If that’s the case then Anakin’s lightsaber should have stopped working because it would have sensed his turn to the dark side in ROTS, or at least should have turned red due to Anakin’s dark side influence, but no, it keeps functioning as normal when used for very obvious dark side actions like slaughtering children.