Color Increase after Feeding

[Bixby'sMenagerie]

So I got several BTAs a few weeks ago and today I decided to offer some chopped shrimp. They all immediately took a piece, the larger ones 2, and I noticed something new. The tips of the bubbles began noticeably glowing from pink to blueish purple. Happened on both the green and rose ones. Is this normal? I thought it was kind of neat but couldn't find any related posts. Cant really see how bright the tips got in the picture.

 

[Deep Dive Aquatics]

I have some corals that noticably color up when being spot fed too. Can't tell if it's the time of day or light spectrum effecting it more or less. It definitely doesn't happen at every feeding though because it's something I look forward to seeing and don't always.