Ah, yes, “reasons”.
- Jedi use Ilum crystals, which only come in blue and green. Sith use synthetic crystals, which only come in red.
- Jedi sentinels use blue crystals while Jedi consulars use green.
- Kyber crystal colours reflect the affiliation/temperament of their users.
Blah blah blah bullshit.
Aesthetics and symbolism are the only valid reasons for any lightsaber colour.
How is it “bullshit”?
Because like most Legends canon, it’s trying to attribute a logical reason to things Lucas randomly decided because he liked the way it looked. 1 makes some sense, which I think is what nuCanon says, but the other two are trying to establish rules that the movies themselves don’t follow. See also: Lightsaber Fighting Styles.
But none of this is relevant for this edit.