What is the source of Dr. Seuss' Green Eggs and Ham? (Why do hard boiled eggs sometimes have green coated or tinged egg yolks?)

Answer 1

The green color is likely due to iron sulfide. The egg itself is the source of the sulfur and the iron may come from the egg OR from iron rich water in which the egg is boiled. I understand longer cooking tends to underscore the green coating of the iron sulfide; less cooking time makes "cleaner" looking boiled eggs.
You know, I've read that story about Green Eggs and Ham to my son for years (he liked all of those Dr Seuss stories) and didn't get the connection between green eggs and iron sulfide until your post (some 45 years after I quit reading to my son). I just thought the title was one of those "Give it a title that will make people by the book."