Alright, so in the OVA I was watching, I seen Levi killing a female titan (prior to the fight with the female titan, Annie), and that female titan's eyes were strangely and abnormally glowing red. This titan was later killed by a raging Levi.
When Levi is in battle with Annie (as seen in the screenshot below), his eyes began to resemble that titan's eyes that he killed from the OVA that killed his friends.
This leaves me wondering. I've been searching around on the internet and seen that nobody has brought this up yet. I thought I would.