Guys, I promise, I’ll get over this wave of Star Wars posts eventually. It’s just on my mind a lot right now.
And something I’ve been thinking about is the physical manifestation of the Dark Side. In Revenge of the Sith, when Anakin turns to the Dark Side, his eyes go bloodshot and yellow. His eyes are still stained like this when we see him partially exposed during his fight with Ahsoka in Rebels. When Luke redeems him and removes his helmet, Anakin’s eyes are soft and friendly again.
Other Dark Siders may have yellow eyes. Darth Maul and Savage Opress both have those tainted yellow eyes. Pong Krell’s eyes are…yellow-ish. And Palpatine’s eyes are the bright yellow of a predatory animal, when he’s not wearing the kindly face of the Chancellor.
But I don’t think we ever see Count Dooku with anything but those dark eyes of his. Snoke’s eyes are not yellow. Asajj Ventress is known for her ice-blue eyes. And Kylo Ren’s eyes have so far remained a dark color.
We could say that perhaps the yellow-red eyes are just visual metaphor, signifying corruption, and not meant to be literally present. However, Dark Disciple confirms that the yellow eyes are visibly present, at least to some. When Ventress finds Vos after his corruption under Dooku, she sees that “Vos’s eyes were no longer a warm, rich brown. They were a blood-rimmed shade of yellow” (185). When Ventress briefly gets Vos to calm, the “yellow hue faded from his eyes,” but that “awful yellow hue returned to his eyes” when her entreaties fail and he returns to his impassioned attack (189).
Interestingly, Ventress later finds Vos without the yellowed eyes but knows he is still corrupted because she still feels “the fury inside him now” (209). Vos eventually admits that he had remained loyal to the Dark Side, that Ventress was correct.
I don’t know if there’s a canon answer as to what causes a Dark Sider’s eyes to yellow. Speculation on Reddit suggests that it is an intense connection to the Dark Side. If so, how would Palpatine not always have those eyes, with his intense Dark Side presence and constant evil hatred and malevolence? I suppose he could mask his face the same way he masked his presence from the Jedi (and this certainly would not be the first time that someone has suggested that Palpatine only revealed his true face after his encounter with Mace Windu, that he was not actually “disfigured” at all then).
My personal feeling is that the yellow eyes represent a loss of control. A Dark Sider strives to control the Force, but some let the Dark Side ultimately control them. For Palpatine, the Dark Side is a tool. For Anakin, the Dark Side is desperation and anger and confusion and fear all being unloaded at once.
What does that mean for Kylo Ren, though? I see Kylo as perhaps the most unstable Dark Sider yet, prone to violent rages and tantrums. But he has constant conflict in him; maybe he has never fully given himself to the Dark Side.
Or maybe this is just an inconsistent element that changes with the story being told and the creative team telling that story.
I bet that there’s at least a partial canon answer floating around in the minds (and files) of the Lucasfilm Story Group. But we don’t have a full answer yet.