Low life opponent champ gets blue lifebar, standing close to another opponent champion

Hi,

came with Zyra to bot lane where the opponent Quinn and Thresh stood near each other. Quinn was low life at that moment (i would estimate about 100-300 HP). For a short amount of time, her life bar was coloured blue as if she was not an opponent. That vanished shortly afterwards and it was red again.

Game Mode: Summoner's Rift, Normal (Team Builder) Date: 15th of October, 2015 Time: somewhere between 1 and 2:30 am. Minute: sorry, I don't remember.