ShadowClawZ's avatar
Well the red in this picture is due to the light from the saber, I'm not really sure the yellow eyes would have been a
good call. They never explained them in the prequels really, it did look cool, but lol not sure why they're really there. I thought the red light reflecting off Kylo's eyes was far more effective when he killed Han, but thats just me. ^~^.
JasonRyder's avatar
It's a sign of immersion in the dark side. 
ShadowClawZ's avatar
I assumed thats what it was ^^ 
JasonRyder's avatar
Odd that Kylo Ren didn't display it after killing Han Solo and fighting Rey and Finn.
ShadowClawZ's avatar
 Truthfully it has to do with different directors. lol Not really any other reason XD 

George Lucas Liked it J.J. Abrams just didn't  use it.