Depending on your plans for them they may turn out to be nice blue egg layers. Just keep in mind that they most likely aren't pure and shouldn't be advertised that way in the future. Doesn't mean they won't make fine layers and good chickens.They are hatched from eBay eggs so there are no real assurances of anything. I'll see how they develop!
If it were me, I would inform the seller that these chicks aren't what they believe them to be. Might help them to improve their stock or at least think twice about selling them as pure. Enjoy your chicks, they look nice and healthy. If you stick around I would be interested to see how they turn out!