When I was deciding on a large fowl breed recently... I love Rocks but wanted maybe partridge or blue and came across this, which sounds to me like what is being described, though I would expect them to call them blah blah blah... Sometimes different hatcheries will call their same cross something else than the next hatchery over.
https://thechickhatchery.com/home/sapphire-blue-plymouth-rock/
http://duncanspoultry.com/sapphire-blue-plymouth-rock-female/
Knowing the actual source could tell you a bit more.. as mentioned above there are other blue birds made from different hybrid crosses. But if it's your only source for chicks... get what you can... pick a variety of chick shades as I suspect them may come all the way between Lavender to smokey or much darker like the Sapphire gems..
https://hoovershatchery.com/sapphiregem.html
I ended up going with Bielefelder since I want to breed them
https://thechickhatchery.com/home/sapphire-blue-plymouth-rock/
http://duncanspoultry.com/sapphire-blue-plymouth-rock-female/
Knowing the actual source could tell you a bit more.. as mentioned above there are other blue birds made from different hybrid crosses. But if it's your only source for chicks... get what you can... pick a variety of chick shades as I suspect them may come all the way between Lavender to smokey or much darker like the Sapphire gems..
https://hoovershatchery.com/sapphiregem.html
I ended up going with Bielefelder since I want to breed them