Gray is super important here, as it seems to reference Gray Jedi, Force users who wielded both sides of the Force, but was neither strictly Jedi or Sith.
The quote seems to be a prophecy of some kind, foretelling a time of light, followed by darkness, only for light to shine again.
Basically, they could shoot lightning from their fingers without wanting to rule the galaxy.
These lines seem to say that balance between the light and dark sides of the Force can only be balanced through a new perspective i.e. “refined Jedi sight.”