The recessive b (Brown) gene is responsible for turning all black pigment on the dog to brown, so a solid black becomes chocolate, and an orange becomes an orange dog with brown pigment, a black & tan becomes a chocolate & tan, and so forth. These dogs cannot have black pigment or hairs ANYWHERE on their body. Their eye rims, paw pads and nose will all be brown, never black.
Chocolate
The solid variation of brown is analogous to a black but with only brown pigment remaining in the coat. They are born solid brown all over. They can range from a lighter brown to a very dark brown.
Beaver (Liver Pigmented Orange)
An otherwise orange dog with liver pigment is called a “beaver” due to its liver/brown pigmentation. It appears similar to an orange but it has liver nose pigment, paw pads and eye rims. There are no black hairs or black pigment anywhere on its body. Like oranges, the shade of orange can vary from pale cream to darker orange.
Beaver newborn Beaver 8 wks Beaver 10 wks Beaver 6 mos Beaver adult Beaver adult Note the liver pigment on eyes, nose and lips
Chocolate & Tan
Chocolate & tan is the brown version of black & tan. It is a solid chocolate dog with a tan pattern.
Chocolate & Tan 3 wks Chocolate & Tan 8 wks Chocolate & Tan 6 mos Chocolate & Tan adult Chocolate & Tan Adult