Liver (color)  At right is displayed the color traditionally called liver. The first recorded use of "liver" as a color name in English was in 1686. Liver may also refer to a group of certain types of dark brown color in dogs and horses. Said nomenclature may also refer to the color of the organ. In dogs, the Liver color is caused by dilution of the eumelanin (black) pigment by the B locus. The gene that causes Liver is recessive, so a BB or Bb dog has normal black pigment. Only a bb dog is Liver. There are several different recessive b genes, but they all turn the coat brown. They are only distinguishable through genetic testing. Liver may also be called different names such as Brown, Chocolate, or Red. Red is a very misleading term, and should be avoided when referring to the color liver because it can be confused for phaeomelanin pigment. This second pigment is what colors all the "true red" or yellow parts of a dog. Liver dilution can also be combined with other genes that dilute a dog's coat. The D locus dilutes black pigment to a blue-grey color usually called Blue. It is a recessive trait like Liver. When a dog has both Liver and Blue dilution, it will appear to be a light, warm-gray color known as Isabella. This is the color of Weimaraners. This color also has alternate names such as Liliac or Silver. When Liver is combined with Merle, the eumelanin (black) pigment is further diluted in random patches. This usually creates a light reddish-gray dog with dark brown patches. This color is often called "Red Merle" even though that is misleading. A more correct name would be Liver Merle or Chocolate Merle. There are many other dog colors that can look like brown, but are not Liver. A dog that is very dark red, like an Irish Setter may sometimes appear brown. Dogs with a blend of Black and Red/Yellow fur can also look like they have brown areas. An easy way to tell if a dog is Liver or not is to look at their nose. Eumelanin (black) pigment colors a dog's nose, so a Liver dog will have a Liver colored nose. If the nose is black, the dog is not a liver. A pink nose has nothing to do with liver dilution, and will not help determine if a dog is liver or not.