This info gathered from http://users.tpg.com.au/choclab/cci/cci.htm
The genetics of coat color is
quite straight forward when you have come to terms with some genetics terms
and principles. DOMINANT & RECESSIVE are terms used to describe genes. In Labrador coat color there are two sets of gene pairs, and the dominant and recessive interplay of these genes will determine the color of the dogs coat. Labrador FactThere are really only two coat colors, Black and Brown. The Yellow dog is not the result of a color gene, but rather the inability to Express a dark coat color. Three principlesFirstly  A Dominant gene will determine the color of a dogs coat if it
is present in the genetic make up, no matter what other gene is present.
And so: Two Labrador Gene PairsOne gene pair will determine dark coat color (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). 
If a Black dog mates with a
Yellow bitch, what color will the puppies be? The answer depends on the genes each parent carries. The way the genes can be passed on is written out following a particular pattern. First the parents genes are written with an x between to indicate a "cross" breeding. eg. BbEE x BBee Second: The genes the parents can pass on is written out into two tables. eg. Taking the example above

bbEE x BbEE
will give the probability of 1/2 chocolate & 1/2 black.
bbEE x BbEe
will give the probability of 1/2 chocolate & 1/2 black.
bbEe x BbEE
will give the probability of 1/2 chocolate & 1/2 black.
bbEe x BbEe
will give the probability of 3/8 chocolate, 1/4 yellow, 3/8 black (a rainbow
litter).
Black to Black Pairings
How do two black dogs produce chocolate puppies? Both must be carrying a
chocolate gene.
BbEE x BbEE
will give the probability of 1/4 chocolate.
BbEE x BbEe
will give the probability of 1/4 chocolate.
BbEe x BbEe
will give the probability of 1/8 chocolate, 2/8 yellow, 5/8 black (a rainbow
litter).
Yellow to Black Pairings
Bbee x BbEE
will give the probability of 1/4 chocolate & 3/4 black.
Bbee x BbEe
will give the probability of 1/8 chocolate & 3/8 black & 1/2 Yellow (a rainbow
litter).
bbee x BbEE
will give the probability of 1/2 chocolate & 1/2 black.
bbee x BbEe
will give the probability of 1/4 chocolate, 1/2 yellow, 1/4 black (a rainbow
litter).
Chocolate to Chocolate Pairings
bbEE x bbEE
will give 100% chocolate puppies.
bbEE x bbEe
will give 100% chocolate puppies. One half will carry yellow.
bbEe x bbEe
will give the probability of 3/4 chocolate pups, and 1/4 pale yellow pups.
Chocolate to Yellow Pairings
bbEE x Bbee
will give the probability of 1/2 chocolate & 1/2 black.
bbEE x bbee will
give 100% chocolate.
bbEe x Bbee will
give the probability of 1/4 chocolate, 1/2 yellow, 1/4 black (a rainbow litter).
bbEe x bbee will
give the probability of 1/2 chocolate, 1/2 yellow with a brown nose.
(Yellow to Yellow will only ever produce yellow.)
All dogs with these genetics will look like this:
All dogs with these genetics will look like this:
All dogs with these genetics will look like this:
All dogs of mine with these genetics will look like this: