It's an off-chance, but I read recently that certain color varieties of OEG have "chipmunk" colored chicks that can be sexed from hatch. These are 2.5 week old crele chicks that we purchased straight run and both have the same stripy markings, but one chick is a darker black/brown and the other is grayer/brown.
Chick 1 (lighter):
Chick 2 (darker, maybe more developed feathers):
Thoughts? Guesses? Wait longer?