A Jedi must build his own lightsaber.
In Star Wars, a lightsaber is never bought. Never issued, never inherited. Every Jedi builds their own, and this is not a tradition. The weapon does not work right any other way.
Why
The heart of a lightsaber is a kyber crystal. The crystals grow on a few sacred worlds. Ilum. Jedha. They hide in ice caves, and they choose their owners: a crystal stays hidden until the right person comes looking, and younglings are sent into the caves to find their own. Nobody hands you one. Nobody can tell you which is yours.
You find the crystal that resonates. You meditate until it aligns with your presence in the Force. Then you build the weapon around it. The saber that comes out is unique, and it moves like part of your arm.
A borrowed crystal feels cold in the hand. Resistant. Unbalanced.
The color
A kyber crystal is colorless. It stays colorless until a Jedi attunes to it. Then it turns blue or green, or in rare cases some other shade. The color is not chosen. It is what the bond between this crystal and this person turned out to be.
The Sith cannot do this
The crystals are attuned to the light side of the Force. A crystal is offered, never taken, and offering is the one thing the dark side cannot ask for. Its whole method is taking.
So no crystal ever calls to a Sith. There is exactly one way for a Sith to get one: theft, or kill the Jedi it belongs to.
And the crystal knows.
A stolen crystal has to be bled. The Sith pours rage and pain and fear through it until it gives in, and it turns red. Every red lightsaber in Star Wars is a crystal that was taken instead of found.
Crystal is Greek. Krystallos, ice, from kryos, frost. The Greeks believed rock crystal was ice frozen so hard it could never melt again. The Jedi dig theirs out of ice caves, and a borrowed one feels cold. The word knew before the story did.
The weapon was never the point. The search was. Skip it and the blade still ignites. It just is not yours.