Luke's Green Lightsaber
Luke's green lightsaber is symbolic of the Jedi and the good they stand for.
Darth Vader's Red Lightsaber
Darth Vader's red lightsaber is symbolic of the opposite: the dark side and all the evil that they stand for.
Hoth
Aside from some of the elements of the Rebel base, Hoth is almost completely white in color. White is one of the most powerful symbols of the world. It symbolizes peace, serenity, and goodness.
Music Motifs
It is music that is the most prominent motif in the Star Wars film series. One of the better-known music motifs is the song called "The Imperial March," which is considered a leitmotif and which is played whenever audiences see Darth Vader or the impact he has on a situation.
Allegory of the Cave
Luke's trip to the cave near Yoda's home at Dagobah is an allegory for what lies beneath the surface in a situation. In this case, that would be Darth Vader's impact on Cloud City and on Luke's friends.