Why Do Eggs Turn Green When Cooked?

a hard boiled egg cut in halfa hard boiled egg cut in half

Why do Scrambled Eggs Turn Green In a Cast Iron Skillet? This harmless but unappealing color change is the result of a chemical reaction between iron in the pan and sulfur in egg whites.
Why do Boiled Eggs Turn Green? The discoloration that sometimes forms around the yolk of hard-boiled eggs is the result of a similar reaction – this time between sulfur in the whites and iron in the yolks.  It too, is harmless.  It occurs when eggs have been cooked for too long or at too high a temperature.  Our method – cooking eggs in hot, not boiling, water, and then cooling immediately – minimizes this.