Labrador Retrievers come in three colours, Black, Brown and Yellow. How does this happen? Why do Yellow Dogs mated to Yellow only ever produce Yellow puppies? Why do some Black dogs only have Black puppies, no matter what colour the other parent is?

The genetics of coat colour is quite straight forward when you have come to terms with some genetics terms and principles.
(If you know this, go straight to the Chocolate genetics page.)

DOMINANT & RECESSIVE are terms used to describe genes. In Labrador coat colour there are two sets of gene pairs, and the dominant and recessive interplay of these genes will determine the colour of the dogs coat.

Labrador Fact

There are really only two coat colours, Black and Brown. The Yellow dog is not the result of a colour gene, but rather the inability to Express a dark coat colour.

Three principles

Firstly - A Dominant gene will determine the colour of a dogs coat if it is present in the genetic make up, no matter what other gene is present. And so:
Secondly - A Recessive gene can only determine the colour of a dogs coat when no Dominant gene is present.
Thirdly - Genes come in PAIRS, where one part of the gene is inherited from the mother and the other from the father.

Two Labrador Gene Pairs

One gene pair will determine dark coat colour (Black is dominant, Brown is recessive), and another pair are Expression genes: the abiliy to express a dark coat (Dominant) and the inability to express a dark coat (recessive).

All this information is better understood if we use a shorthand way to represent the two sets of gene pairs.

B - black coat colour      b - brown coat colour

E - able to to express a dark coat       e - unable to express a dark coat

By convention, the dominant gene is shown in upper case, the recessive in lower.

A coat colour gene looks like this: BB or Bb or bb

An expression gene looks like this: EE or Ee or ee

The interplay between the dominance issue and the two gene pairs will determine the colour of the dogs coat.

Click here for more detail on coat colour genetics.
All the different ways you can be a labrador - the list.