"Colour" does not have to equal "alignment".

Apprently, Rich chose it to be this way in his world. Legit. Understandable. Could have been othervise, was not, there are no objective reasons for or against. Choice of style. Personal preference matter. I like it. Next.

Unavoidable Star Wars Example: A red lightsabre does not have to indicate the wielder is an evil sith. Can. Might. But does not have to.