EDIT: I posted before Googling it, because I assumed it would just give me Naruto results. Turns out it took me to this browser extension. Thanks for sharing!
Edit again: Now I'm extra dumb because that's not even from Naruto.
Shinigami are a general Japanese concept. The soul reaper's from bleach were also referred to as shinigami. Basically kami/spirit of death. I did watch death note aeons ago. And the character attached to the death note was also a shinigami. Though I don't remember anything special in reference to it's eyes? Meh I probably just missed it or forgot. Its been almost 20 years XD
The eyes tell you how many days someone has left in Death Note.
So if someone shows up as red they’re more likely to be an antivaxxer as they’re more likely to be ignoring science, their days are going to be fewer as a result of their ignorance.