A noteworthy aspect of this blue lighting can be seen towards the end of the film, where Deckard shoots Priss, another of the escaped replicants. In other scenes, Priss, being a "basic pleasure model", is portrayed under a natural light used to bring out her beauty. The moment Priss gets shot in the scene where she attacks Deckard, she begins to writhe demonically in the same blue lighting that we often see Roy in (1:33). In later scenes, where Roy is about to commit something heinous, he will often be put in an environment where the lighting comes from below, casting shadows under his eyes and creating a rather ominous feel for the scene (1:20). In Roy's final moments however, he saves Deckard's life by pulling him up from what would have been a fatal fall. He sits down next to him and begins to speak his final words, and in this scene we see Roy in a different light; with the large neon signs beaming behind him, Roy is exhibited with half his face in darkness, the other half in light. This symbolizes his true nature, a replicant that would go to any lengths to preserve his life and the life of his loved ones. The rainwater on his face makes the light shine brighter, so that Roy looks almost angelic, a twist on a character that would have otherwise been deemed demonic. .
The protagonist of the film, Deckard, has his own lighting scheme as well. This functions in a number of ways. On screen, Deckard has light behind him, so that half of his face is always cast in shadow. There are heavy implications throughout the film that Deckard himself is a replicant, and the duality of his lighting tends to accentuate this. Off screen, through the "lens" of Deckard's character, the lighting is dim or dark. Dark lighting forces the viewer to focus more on the details close to characters. Since the entirety of Blade Runner is viewed through the lens of Deckard's character, this is a deliberate choice.
