Neither one is a true breed. Those are what I consider marketing names, no legal requirements behind them. In some cases it is Buyer Beware so I don't know how reliable anything is on yours. I don't know who your breeder is or how good they are. I have never had either, I'm getting most of my information from the internet and we know how reliable that is.
Mystic Marans were supposedly developed in the Czech Republic by crossing Black Copper Marans with Barred Rocks. You can get some variation in appearance since their ancestors were crosses. They are supposed to lay a lot of eggs, probably pretty dark brown. Something that does not make sense. The hens are supposed to be fairly small, about the size of a Leghorn. The parent breeds' hens are larger. I'm not sure why the Mystic Marans are so small. Still, they should be attractive chickens that lay a lot of dark brown eggs.
Information is a bit more mixed on the Sapphire Sky. Supposedly they are a cross between Barred Rocks and Blue Rocks but again the Sapphire Sky are too small. Also the Sapphire Sky have a crest which Rocks do not. And Rocks lay brown eggs where the Sapphire Sky mostly lay green eggs. Some hens lay brown eggs but most seem to lay green. I've seen where Crested Legbar may be in their ancestry, that would make a lot of sense. With their mixed and mysterious ancestry you can get some surprises but for the most part you should get a hen with attractive feathers that lay a lot of usually green eggs.
If your interest is in meat chickens or showing chickens these are not for you. But if you want attractive hens that lay a lot of relatively large eggs and usually are well-behaved in a backyard flock I think you made some good choices.
