space: next costume lore: in this universe, a curse had been inflicted that gave certain monsters and humans 3 lives, with one catch, they would be aggressive on their last life. Sans was one of the ones to be inflicted with this curse. his eyes now show what life he is on. (Green = 3. Yellow = 2. Red = 1.)
based on: https://the-life-series.fandom.com/wiki/The_Life_Series_Wiki specifically, 3rd life
