Health Bar Damage

[Draenic]

I can't seem to understand a certain health bar visual. Sometimes when I take damage or deal damage, the damage done on the health bar would be darkened for a bit before ticking off. I thought this might be a 'fight back' mechanic similar to Bloodborne where I could regain some of the health lost by doing damage. Anyone know what this change in the health bar visual means?

[chicken]

I think it's just to give a more visible indication of how much damage was done by the last hit you took.