So if a kyber crystal is colorless until selected by a padawan or Jedi, at which point it becomes a color that reflects the nature of its owner, why does it seem to settle into one of two shades almost every time?* It's either that particular green or that particular blue. Sure, there are exceptions like Mace Windu's purple blade (and lots more in Legends/EU), but "mainstream" lightsabers are always either the green or the blue. In theory, couldn't they be any color within a certain range? Why couldn't you have a teal or a cyan lightsaber?
The apparent out-of-universe reason would be that the concept of how a lightsaber gets its color wasn't fully developed by the time the movies were made (or perhaps that, within the context of the films, it's an insignificant detail), but does anyone know of a reasonable in-universe explanation for this?
*I'm referring specifically to the natuarally-ocurring crystals used by Jedi lightsabers. Synthetic and Sith-modified crystals significantly expand the scope of the question and introduce a lot more complexity, so at least for the time being I'm ignoring those.