If you boil eggs too long or use heat that�s too high, it will make a green ring around the yolk. This is okay to eat, but it doesn�t look very nice. Boiling at a lower temperature will solve the problem...or place the eggs in an ice-water bath when the eggs have cooked the proper amount of time.
It could well be associated with the chicken's diet. This is more likely to occur if they are free-range when hens can forage for different food. Chlorophyl, if eaten in sufficient quantities especially in Spring, can make the white of an egg greeny colour. I've seen a similar effect in geese who were fed a diet of carrots one Winter when not only their eggs became pink but the geese themselves took on a pinky colour. In the same way flamingoes turn pink after eating shrimps.
Thank you, yes i think you might be right about the feed, ive been doing a little searching and it could be due to high levels of riboflavin (B6) in feed and in fresh eggs its not a bad thing, just doesnt look too good.
That link is interesting. If true, then it yet again shows up the programme "QI" for its lack of research, since Stephen Fry was armed with the claim that no flamingoes are pink due to eating shrimp. He said it was due solely to eating algae.