But nope. Red = bad & everything else = good for stupid EU reasons.
“you’ve constructed a new lightsaber. Your skills are now complete. Now join me, throw this away, and build a red one.”
LOL!
Even when I subscribed to the “darksiders use red” school of thought, I never once thought there was any big in-universe rationale behind it; I saw it as symbolism, pure and simple. I imagined if Luke had turned to the dark side and joined Palpatine, he would’ve kept using his green saber unless/until he lost it or it was destroyed.