So, we know the production reason the new lightsaber is green is because it stands out better against a blue backdrop.
But that aside, where the hell does Luke obtain the parts--particularly a kyber crystal--to build it? We know that the Empire had occupied Illum, so he can't go there and have the crystal choose him. So where does he get one?
Does Obi-wan just have spares lying around? Or did he scavenge Qui-gon's green crystal for Luke to use later?
Or does Luke
buy Cere's crystal from the black market?
What do we think?