I've noticed sometimes when I hit enemies their life bars stay filled in but red, instead of draining to black. In the current case it's a team battle. I've seen similar happen in other fighting games where part of the health bar is "damaged" but sticks around until you can finish a combo/etc, but in this case the red bar doesn't appear to go down if I stop attacking. When the red reaches the end of the character's health bar, they still go down. I've also noticed some attacks deal both "black" damage that drains immediately and some "red" damage that doesn't drain until the opponent is KO'd.
What's the purpose of the red, "sticky" part of the health bar? Do characters have an opportunity to gain some of that health back? Do some attacks/circumstances cause "red" damage instead of "black" damage?