Throughout the story of Star Wars, there are many Sith, the evil lords of the galaxy. Their corruption to the dark side of the force changes their appearance in many ways including the vicious yellow eyes. Sith show this change except for Darth Tyranus (Count Dooku) and Kylo Ren. But why don’t these two Sith have yellow eyes?

Count Dooku was the leader of the Droid army and once an apprentice of one of the most powerful Sith lords. So why doesn’t he have the appearance of a Sith? The answer is Count Dooku turned to the dark side because of political issues in the Jedi order and the Senate. He doesn’t completely use the dark side, therefore he doesn’t have the aspects of a Sith. Kylo Ren on the other hand struggles with using the dark side. This may explain why he also does not have the appearance of a Sith.

Safe to say that not all Sith completely embrace the dark side. Therefore the aspects of a Sith, including the iconic yellow eyes, don’t belong to every dark lord.