Originally Posted by double-a-ron
btwno matter what you try, you wont end up with an entire litter of one color.
labs, one of my favorite topics...
You *can* know that the litter will be only one color, but it depends on the genetics of the parents, which usually isn't known until they've had multiple litters. I used to use lab coat color as a genetics problem in a biology class I taught.
First set of genes determines if the dog is dark (black or choc; dominant) or light (yellow; recessive). If it is a dark dog, the second set of genes will determine whether it is black (dominant) or chocolate (recessive). If the dog is determined yellow by the first set of genes, the second doesn't come into play on what color it is, but is important for what it can pass onto offspring.
A great site to explain it is at: http://www.blueknightlabs.com/color/coatcolor.html
...you can actually simulate different genetic matings and see what the results will be (statistically at least). Of course all breeders know that when you really want a litter half yellow, half black, they'll all come out black! If you do the choc x choc simulations on this website, you'll see that in all possible combinations, you'll end up with a litter of entirely or mostly chocolate pups, so that's a good plan if you want chocolate pups. And it is impossible to get a black pup out of two chocolate parents... that would be like getting a brown-eyed baby out of two blue-eyed parents - impossible unless the mailman is involved. For me, picking a good temperment match in a stud would be way more important than coat color.
I'm always amused when people claim that "yellows are mellower," "chocolates are dumber," etc.! It's just hair color! There's no evidence that coat color is in any way linked to smartness or personality...
One last thing, before purchasing a purebred lab, ask to see certificates of hip dysplasia screening for both parents (involves x-raying hips and evaluation by a orthopedic vet). Elbow screening is good too.