If you are breeding blue chickens, they will never breed true because of the genetics. Breeding blue birds to blue birds you will get 50% blue, 25% splash, and 25% black (partridge). A blue male over black hens will produce 50% blue, 50% black. The only way to always end up with all blue chicks is to put a splash male over black hens for 100% blues. Getting and keeping the lacing pattern correct will be even harder, as the blue genetics can really mess that up.
To actually address your question about the cockerel's chest color, all the roosters I've seen have had solid blue chests. However, I am curious to hear from an expert if the laced chest is also acceptable.