The term Gray Jedi has it’s origins in the KOTOR character Jolee Bindo. Maybe Qui-Gon Jinn. But what made both of them to be considered “Gray” was simply questioning Jedi orthodox thought rather than embracing powers or ideas of the darkside. The fact that fandom decided that disagreeing with authority qualifies you as “gray” says a lot about Star Wars fandom. Jolee’s best quote:
“Love doesn’t lead to the dark side. Passion can lead to rage and fear, and can be controlled, but passion is not the same thing as love. Controlling your passions while being in love, that’s what they should teach you to beware, but love itself will save, not condemn you.”
Take that Yoda!