Look for green legs and little muffs or beards on their chins,, it is usually a good indicator.
My question would be who hatched them,,, yourself? Or another party? If you hatched them yourself and they came from a green/blue egg it will definitly be an EE as the green/blue egg coloring is a Dom gene trait. However,, and I hate to disapoint you,, that doesn't mean that you will get green/blue eggs from them. Chances are you will,, but due to the all the cross breeding that was done to the breed (i almost hate to use the term breed because they really are the mutt of the chicken world) you may end up with just a plain brown egg layer.