When Christensen raised the idea behind the scenes, arguing that it served the necessary purpose of signaling Anakin’s character change to the audience, it took Lucas a few days to come around. As Christensen explained to Empire Magazine:
“George was initially against the idea when I brought it up. I loved the visual of Sith eyes and thought it could make sense: Darth Maul had them and Sidious has them. George responded saying that Count Dooku didn’t, and I thought that was the end of that.”
The logic seemed to be that the more human-looking the Sith character was, the less fitting those evil eyes were. Darth Maul could have those creepy eyes because he wasn’t human to begin with, while General Grievous could have those unsettling yellow eyes because he was already a robot. But how would one explain how Palpatine has yellow eyes in the original trilogy, but blue eyes in the prequels? The logical explanation would be that eye color can be altered by the dark side and that the only reason Palpatine had blue eyes in the prequels was because he was disguising them. Palpatine actor Ian McDiarmid has even argued that the character’s appearance for much of the prequels was basically a mask, and it seems his eyes were no different.
“A few days later [Lucas] came back to me and said he thought about it some more and now liked the idea of Sith eyes,” Christensen continued, “but not for that scene.” The scene they were discussing was the one where Anakin chops off Mace Windu’s arm; instead, Anakin’s eye color change was moved over to the sequence where he murders the Separatists hiding on Mustafar.
