He might be talking about Blue Andalusians. In size they are bigger than Leghorns, about the same as Minorcas.
A unique genetic feature of this breed is the constant recurrence in the offspring of not only all blue chicks, but also the black, white, and black-white colors used in the original matings many generations ago to produce these blue birds. All of these chicks carry the blue genes and when mated black on white .
Approximately 50% of the baby chicks will be all blue. The other 50% will be black, white, and black/white combinations.
Most hatchery's have them.