Why were the colours of lasers inverted in Star Wars? (Out-of-universe!)
In A New Hope (ANH) and The Empire Strikes Back (ESB)
We know why the colours of lightsabers were chosen as blue for the Jedi (Luke and Ben), aka "the good guys", and red for Darth Vader, aka the bad guy. In ANH and ESB these were chosen mainly for political reasons:
Out of universe, the Blue / Red distinction was made during post-production when the lightsaber blades were being rotoscoped, as the original blades were simply white. The color choice might have bean influenced by the political climax, the red color being traditionally associated with Soviets and blue with Americans, but also note than the colors reversed for blasters and spaceships.
In Return of the Jedi (RotJ)
He goes on to explain the reason for Luke's green lightsaber in RotJ, which was made for technical, not political reasons:
Luke's green lightsaber was added late in post-production of the Return of the Jedi in order to better stand out against the blue sky of Tatooine in outdoor scenes. So all those signification / explanation are all retcon.
Laser Colour (In-universe!)
The second link in the first quote gives an in-universe answer as to why the colours of the lasers used by ship's and hand-carried lasers are reversed. I.e., imperial lasers are blue-ish/green-ish while rebel lasers are red:
If I recall, the color of a blaster bolt (character-scale or starship scale) is determined by the quality of the gas used in it - higher quality gives you green, lower quality gives you red. The Rebellion didn't have access to the highest quality gas, and had to make do with the lower quality ammunition.
Laser Colour (Behind the scenes reason)
Now, given that background information, there must be a good reason for the directors to have decided to reverse these colours and I cannot help but wonder what significance that has. The reason that is provided as an In-Universe explanation is very obviously a retcon for the choice that was made when post-producing ANH.
I'm asking for the original reason and the allegorical interpretation of the symbolism of these colours.