here are a variety of eggs. The darkest ones were laid by the broody setting on the clutch. She is a copper black marans. She is my darkest egg layer. The other eggs are RIR, Ameraucana (or EE) Silky, and bantam cochin eggs.
Here's some different ones for comparision. The black/blue copper eggs are from Bev Davis. My RIRs lay a fairly dark egg too. Don't know the Cuckoo lines, but they aren't quite as dark as the BC Marans in person.