I have had one Welsummer lay very dark eggs, one lay the lighter eggs with blotches, and several Welsummer crosses that laid just regular brown eggs, which the breeder fully expected as the dark brown is not dominant.
The dark brown wash is pretty complicated genetics, and once you've lost it in the hen, she won't be adding it to her offspring.
It has been my experience that once lost, it doesn't throw back...but I am just starting my dark egg breeding program.
I've read that typically you get a middle road if you breed dark to light...a middle tan. If you breed light/splotchy to dark??? I don't think you'll get dark.
I remove those hens from the breeding as I don't won't that cropping up in my dark line.
Edited by Lady of McCamley - 1/15/16 at 4:19pm