I’m trying to think when/if we’ve seen gold magic elsewhere, and I’m not sure if we have.
I’m wanting to say that when Robin used the fairy wand, I think it glowed gold?
I did love that the magic that came about when Belle was doing stuff that had been set up by Rumple, that it was gold of all colours.
I’ve always got the TinkerMomma theory tucked away in the back of my mind, even if I’m not fully subscribed to it, but I just can’t fully let it go either. As things stand right now, with Belle’s known parentage being 100% genetically mortal, I’m inclined to say that she isn’t especially magical herself.