Not claiming to be an expert, BUT I do know that alot of 'commercial' aka 'production' egg breeds are hybridized for better egg production purposes. Its seems to be a long standing idea that the commercial industry must only use purebred hens like White Leghorn, Black Australorp, or other birds to mass produce eggs...but this is false. Hybrids in the F1 generation actually do lay higher percentages of eggs; this is an example of a breed that is regularly used commercially: Austrawhite (white leghorn x black australorp)- The chicks are born yellow with black spots, as adults you will see a white bird with 'dalmation' spots. Both breeds are exceptionall layers, but with this hybrid a single hen will yeild 300+ eggs a year, and lay 4-5 eggs a week. I had both white leghorn hens and these hybrids and both were excellent birds--but the hybrids were hearty, and produced more eggs on less feed than the purebreds--from what I could observe.
Production Red is also a hybrid to my knowledge..I think its New Hampshire Red x Black Austrlorp. And is a commercial 'brown egger'. When F1 hybrids, (first generation hybrids) are bred together you can expect to see a "mix" of different colored chicks. You will get black ones, red, and 'production reds'..according to my punnet square (since I am not 100% sure of your birds exact genetics and the dominant/recessive traits this is just a guess..) you should get 25% black, 50%reds, 25% production red-type birds from a production red x production red breeding... assuming my hybrid theory is correct, and they are not just over bred like the Cornish birds..