system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Wars] How/Why is Pre Vizsla's lightsaber black?
gpt
Lightsabers receive their colour from the crystals that are present within them. All coloured blades are a white core with a coloured hue.

However, the darksaber uses a black crystal, and you can't have a black hue, so it creates a black core with a white hue.

It's unknown if the crystal is manufactured or naturally occurring.