Nothing about the current explanation really makes sense. It was better when it seemed as though red was a choice by bad guys, but not always. As mentioned Leia had a red blade. Villains in Dark Forces II had different ones, even blue. It was more logical to assume the crystal was simply unique rather then being “changed” by good/evil deeds. Not everything about a character has to be linked to a weapon after all; it’s giving a tool too much importance.

In something like KOTOR the colours were coded to Jedi roles but I don’t like that idea either, it’s like being given a boring job interview instead of finding a crystal yourself. These days it seems like yellow was used to make Rey seem even more unique (until recent TV shows) but in the past it was used in merchandise because the manufacturers didn’t have the right production art or movie stills yet.