I think it's closer to a 1 in 16 chance of looking like a Delaware.
The other possibilities would be:
1 in 16 chance of silver columbian (like Delaware but without the white barring)
1 in 16 chance of red columbian (like a Rhode Island Red or New Hampshire)
1 in 16 chance of barred red columbian...
Not a new breed, just a mix.
Black Sexlinks are a hybrid (a cross of two different breeds). Because they are mixes, their chicks do not always look like themselves.
Black Sexlinks are often from a Rhode Island Red rooster with a barred Rock hen.
When Black Sexlinks are bred to each other...