‘Was Luke’s lightsaber originally BLUE in Return of the Jedi?’:-
https://www.youtube.com/watch?v=nTsnuW2j4Yo - from HelloGreedo
^ Includes Kazanjian, Marquand, Kasdan and Lucas and in conversation about the lightsaber colour - and potential letters over it in Starlog magazine… and the deleted scene from Return Of The Jedi showing Luke tinkering with the new green lightsaber.
A more in-depth article on the subject (and conversation between the four people above discussing it) can be found here…
‘The real reason Luke Skywalker has a green lightsaber’:-
Edit: and this curiosity video in 2009 - from an old friend…
‘Return of The Jedi - Blue Lightsaber Tests’ - https://www.youtube.com/watch?v=WSD8sYRvZ3A - from davnes007