“Mr. Lucas, what gives a lightsaber its colour?”
"Lightsaber colour is determined by the psyche of the person who builds the lightsaber. For example, if a Force-sensitive’s favourite colour is yellow or they have a generally sunny disposition, their lightsaber’ll turn out yellow.
“Why, then, do the Jedi generally only wield blue/green lightsabers and Sith only red?”
“Well, once upon a time, back when the Jedi and the Sith were one religious order, they all wielded lightsabers of various colours and hues. Once they went their separate ways, however, blue & green became associated with the Jedi and red became associated with the Sith, and so gradually their lightsabers came to reflect this.”
“So in effect you’re saying the contemporary Jedi/Sith Orders are both insular cults wherein individuality goes to die, thus explaining the dearth of spectral diversity?”
“Exactomundo.”
“Mr. Lucas, is any of this canon?”
“No, but it should be.”