‘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’:-

http://www.forcematerial.com/home/2016/10/23/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