Hi Katy,
Sorry, I misread your post and thought you said you got a black instead of blue. I was up too early watching chicks! (the fluffy kind) Regarding the egg color vs. cuckoo, it all depends on the line. From what I understand, the copper blacks have had better color set than the cuckoo but unless you can see a sample of the eggs from a particular breeder, you never know what you will get. Unfortunately, hatchery stock can be very disappointing. This is really frustrating, I think, as they will still advertise them as dark egg layers and beginning poultry keepers (their biggest customer group), won't know any better. I just hate to see people be disappointed as I have been there myself. In any case, the dark eggs always seem to be a holy grail that anyone working with the breed is striving for. Even hens that lay good color go up and down in intesity. My avatar shows average egg color from my hens next to a RIR egg. Sometimes they are darker, sometimes lighter. It is always a matter of hatching out the darkest and choosing the most consistent dark laying hens.
Richard