attack lighting issue

I was in a cave and I saw a zombie

What I expected to happen was...:
They usually turn pink/red when attacked

What actually happened was...:
They did turn pink/red, but it did not look how it would usually looked, the lighting for it felt wrong.

Steps to Reproduce:
1. Take any mob, and put them in a dark room
2. Attack them
3 They will turn pink/red, but wrong