maybe not Cadmium. Mercury is, though, https://en.m.wikipedia.org/wiki/Merbromin https://en.m.wikipedia.org/wiki/Merbromin - and on the "paints & coatings" sid

maybe not Cadmium. Mercury is, though, https://en.m.wikipedia.org/wiki/Merbromin https://en.m.wikipedia.org/wiki/Merbromin - and on the "paints & coatings" side, orange-red and anti-rust often enough used mercury salts as well. Rarely these days, fortunately. In some ways, it's nice GaN "won" for blue LEDs. CdTe / CdSe would literally have been "twice bad".