It is impossible to buy silver Labradors online because the silver color is not an available color within the Labrador breed. It is possible, however, to buy black, brown or yellow Labrador retrievers online by selecting a breeder through the American Kennel Club website.
It is usually advisable not to purchase a puppy online because many puppies that are sold online are through puppy mill breeders. Even if it is known that the breeder is reputable, it is always better to visit the puppies in person to get a feel for the breeder as well as an understanding of the puppy's environment. There is also a possibility that an online buyer might be scammed and might not ever receive a puppy.