The big secret of Star Wars is that it's exactly as inconsistent as Star Trek or any other decade-spanning science fiction franchise, the only difference is that Star Wars is ashamed of it for some reason.
Canon is almost entirely up to the era, the realities of the given medium, the writer, and however much policing George Lucas/Lucasfilm felt like doing at that moment. Juhani couldn't be lesbian in KOTOR but now some gay extras in EP 9 are okay. Hyperspace mechanics are basically plot magic that puts characters wherever they need to be. The Force can do whatever the writer says, which has ended up being anything and everything including ghosts, lightning, healing, weather, moving rocks, ships and planets, vampirism, zombies, electricity, resurrection, astral projection, miraculous conception, and more that I can't recall at the moment. Are there Mandalorians left or are they extinct, and are they a race, religion, ethnic group or nation? Why can lightsabers be blocked by mere metal in books and games, but never ever in the films? Do blasters require ammo or not? Is the Force just a natural phenomena, or does it have a personality and will similar to a god? Are the Sith a necessary part of balancing the Force, or is one side supposed to wipe out the other?
Pretending canon ever mattered, or even existed, for something as minor as lightsaber color is just wankery.
Besides, all the Jedi (that anybody cared about) are dead and all the Jedi books are toast, so there's simply nobody left to tell Rey she can't have a yellow lightsaber.