I haven't a clue how the white ring around their necks and tail fan will present in the offspring.
Comets have Dominant White (turns all black to white.) But because they are a hybrid, there is a very good chance that they only have one copy of the Dominant White gene. So half their chicks would get it, but the other half of their chicks would have black markings like you want.
Most of the red sexlinks (like your Comets) have a Rhode Island Red father, so that's one half of what they'll be adding to your chicks.