You can get dark egg color from any variety of Marans. You also can get light egg color in any variety of Marans.
The bottom line here is that any breed that has a lot of color varieties will have one or two mainstream varieties and the rest will tend to be rare colors for the breed . The Leghorn for example has about a dozen recognized varieties in the world, but The white and brown variety are the mainstream ones. You will frequently see a white or brown leghorn on Champion Row at a large poultry show but are not likely to see a buff leghorns or a silver duckwing leghorn ever make its way to Champion row. The reason is that there are lots of people working on the white and brown varieties and their quality has improved. The other varieties have fewer numbers and fewer breeders. Their type is typically not as good and neither is their production, vigor, etc. They are often crossed with White's or Brown's to improve their quality, but you will never see a brown or white crossed with a red leghorn or mille fleur leghorn to improve it.
The same is true for the Marans. World wide the Black Copper Marans is the variety that has the strongest numbers. It is the variety that sets the pace in quality for the breed. Many of the flocks of other varieties were create from BCM lines. As the BCM variety improves it paves the way for the breed to improve. The Black Copper variety doesn't always win the Marans Egg contests but it is held to a higher standard. When I started with the breed I was told that for the BCM variety you needed to require #5 or darker egg from your hens, but that all other varieties you needed to require a #4 or darker. That was not a set in stone rule but shows the level that the BCM is held to in the Marans breed.
