Kog'Maw Bug?
I played a game with Kog as soon as his new Battlecast skin was released
some time in, the enemy Kog had Red Buff we fought, and I died, but then my passive explosion killed him also
when I spawned, I had the Red Buff (minus the time that I was dead)
after it expired, I still had the visual red ring indicator around me
I got our Red and once again, the visual effect lingered after that one expired
In my screenshot you can see the indicator around me and also on the left you can see that I have no Buff listed (besides one Aspect of the Dragon)