I'll have to take a pic. Some of the eggs are a little darker than the others, but they're no where near as dark as Sue's marans.
I had some CM's once and they were ok. Sometimes I think there is a trade off between color and productivity. Not to mention Barred and Cuckoo patterns are auto sexing. This is the reason for the Rhodbars and such.
Next to an EE green or blue I'm sure they look dark enough.

I'm happy with mine laying a xtra large egg and dark, rather than a smaller but darker egg.