"I'm leaning towards it being an interaction with the airglow layer which is lowered due to gravity waves. I know that in heavy thunderstorms , gravity waves form in the airglow layer with deeper peaks and troughs and that the strongest nightglow emissions occur mostly in a relatively thin layer of atmosphere between 85 and 95 kilometers (53 and 60 miles) above the Earth’s surface. Little emission occurs below this layer since there’s a higher concentration of molecules, allowing for dissipation of chemical energy (via collisions rather than light production). Likewise, little emission occurs above that layer because the atmospheric density is so low that there are too few light-emitting reactions to yield an appreciable amount of light. I think that gravity waves perhaps caused deeper troughs pushing this layer of atmosphere associated with airglow down enough to interact with the sprite tops. Then it's a matter of only the most energetic sprites triggered within this trough produce the effect. It would explain why not all bright sprites have this and how not all tips have it in one bright event. Essentially like a tiger elve version of a sprite. Tiger-sprite. My pic of gravity waves in Texas airglow shows similar color."