Scrambled eggs may turn green if cooked in a cast iron pan, or if you hold them over heat for an extended period time, such as in a serving line or buffet. This is due to a chemical process that occurs between iron and sulfur. The color change may prove unappealing, but it's harmless, according to the Incredible Edible Egg.org. If you don't want your scrambled eggs to turn green, you can take some precautionary measures.
Use fresh Grade AA or A eggs when cooking. They are less likely to turn green, according to the American Egg Board.
Whisk in 1/4 tsp. of lemon juice for every 18 large eggs you use when making scrambled eggs.
Use stainless steel equipment and utensils when cooking.
Hold the eggs over heat that is 140 degrees Fahrenheit and above when using a steam table.
When making a few servings of scrambled eggs, add a dash of lemon juice to prevent greening.
Liquid egg products that contain citric acid will prevent greening.
According to the Professional Chef's Association and the American Egg Board, eggs should not be held over heat for more than one hour.