The Labrador retriever comes in three different colors: yellow, chocolate and black. Any other color is not acceptable according to the AKC standards for the Labrador retriever. Occasionally, you may see some slight variations of the three colors such as brindle, black and tan or gold, but these colors are unacceptable as true Lab colors. A yellow Lab, however, may have some different shades of yellow which range from tan to gold to reddish fox. The majority of them are just yellow, however. Some breeders may even advertise a "rare" Lab color. It's rare because it shouldn't be part of the Labrador. You may occasionally see white markings on the chest, but these are the only variations allowed according to the AKC Labrador Retriever Standard.
Dogs have dominant and recessive genes, which determine what colors they will be when they're born or reach adulthood. Black is the prevalent color of labs because there are more black any other color and because breeders appear to like black best. When Labs started, they were black so that color gene is present, with yellow Labs next and then chocolate Labs. Black Labs have two genes, which are responsible for the puppies being black. A puppy can have the genes of chocolate but still be black. They get half of their color genes from one parent and half from the other. If you bred an all black Lab (with no chocolate genes) with a chocolate Lab, you would have all black puppies. Some may wonder why there were no chocolate puppies when one parent was chocolate. The reason for this is that half of the color genes came from each parent, and if one parent has no chocolate genes, there can be no chocolate. However, one of the black puppies can be bred to a chocolate lab and there may be some chocolate puppies because the black puppy does have chocolate genes.
Sounds complicated? It's really quite simple once you understand a little about genetics and the gene color pool in dogs. This is why the black gene is the dominant one and the chocolate the recessive.
When dealing with the yellow Labrador, a third gene is entered into the picture. The future puppies of can have no yellow genes, can be black or chocolate and still carry the yellow gene, or they can be yellow. This would probably explain why there aren't as many yellow Labradors as other colors. The yellow Lab, which is very popular, may have a black or pink nose. Breeders frequently use the gene color pool for breeding when they are hoping to get a specific color of Lab in the puppies.
Some breeders have developed what they call"silver" Lab, which is a lightly colored yellow or chocolate. Silver is not recognized by the AKC or by the Labrador Retriever Club, although some have tried to register this (often unsuccessfully) as chocolate.