We don't have any breeders or experts on parrotlet genetics in this forum. You want to be very knowledgeable on genetics before attempting to breed parrotlets. Good breeders know the genetics of each of their birds and pair them with that in mind.
A turquoise bird is an incomplete blue. It is not recommended to breed blue series birds with other blue series birds as it can result in genetically weak offspring prone to congenital defects. White birds are also blue series birds. The best breeders always breed blue series birds back to the dominant green series to ensure that all of the babies are healthy and genetically sound.