The Labrador Retriever, Labrador or just Lab, is a medium-large breed of retriever-gun dog. The Labrador Retriever, Labrador or just Lab, is a medium-large breed of retriever-gun dog. The Labrador is the most popular breed of dog in many nations. A favourite disability assistance breed in many countries, Labradors are frequently trained to aid those with blindness or autism, act as a therapy dog, or perform screening and detection work for law enforcement and other official agencies. Yellow Labradors are determined at the E locus, so the K locus is irrelevant in determining their colour. Variations in numerous other genes control the subtler details of the coat's colouration, which in yellow Labradors varies from white to light gold to a fox red. Chocolate and black Labradors' noses will match the coat colour.