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 ...

Anakin's first blue lightsaber was broken in Attack of the Clones. Anakin wielded Count Dooku's red lightsaber, showing signs of his growing darkness before becoming a Sith Lord. Although Anakin ...