From my research, the Croad langshans are supposed to be a dark egg layer bred for the extra heavy coating on the egg, so you're right on with that. Like other breeds where egg color matters, I suppose the roosters egg color would be important, which is hard unless you start with hatching eggs. I've also read that it can't be bred for reliably, so I dunno. I've got three wyandotte eggs in my bator right now out of a set of 15 that have the extra coating, making them pinkish. I'm going to separate them if they hatch just to see if any are pullets and whether their eggs are the same.