Question

The red and green colors were used in Return of the Jedi because they had a better "pop" on screen. Why is that?

Answer 1

Compared to the somewhat muted backgrounds of the forests and deserts in Return of the Jedi, bright red and green lightsabers created a visible effect on the way viewers perceived the action.

Besides the significant contrast between the lightsaber colors and the backgrounds of the film, red and green are examples of complementary colors, which contrast with each other when close in proximity.