Boiled eggs with some green around the yolk ... yolks from turning green is to stop the cooking process before the eggs overcook (when the sulfur and iron reaction takes place).

it’s actually safer to eat overcooked eggs rather than undercooked eggs, which can harbour bacteria.” Though the egg might technically be a little safer, most boiled eggs are good to eat.

These combine together when boiled, and if the egg is boiled at ... “The ferrous sulfide that’s formed when the egg is overcooked is actually the same form of iron you find in iron supplements ...