This mod replaces the in game lightsaber weapon by Luke Skywalker's one.
Unfortunately, looks like the slash effect for the lightsaber is colored purple through game code, as I've only found one set of slash sprites in yellow color.

To install this mod you got to use SOR4 Explorer.

Uncompress the mod files somewhere at your hardrive.
After loading SOR4 Explorer, and reading the game files, navigate in the left panel to: / > animated sprites > sor4 > weapons > lightsaber
Here you will drag and drop the four .png files in SOR4 Explorer right panel.
In the top right corner you will see a message saying 4 sprites were replaced. Apply.

Note: I'm adding to the download section the original sprites, just in case you want to revert back, without removing all your mods.