In the original trilogy, George Lucas wanted Luke to be pulled by the Dark Force in each movies, more and more dangerously.
For that, he used a metaphore in the color of his vests: From pure (white) close to be dragged to the Dark Force (Black).
The layout is from iconic sets from each films:
SW4 - Interior of the Death Star
SW5 - Carbonite chamber in Bespin
SW6 - Emperor's Throne Room