Beautiful dogs!
I found this information:
Genetics Of The Black German Shepherd
The black coat gene color can either be dominant or recessive. This means that there is a possibility that a German Shepherd that is not all black can hold the gene and produce solid black German Shepherd pups. If you are interested in breeding your Black GSD, you should inquire about your dog’s ancestry and blood line. A German Shepherd’s coat color can be determined as early as seven to eight weeks old.