First off there are only 3 reconized colors BLK, YLW and CHOC. Theres a lot of speculation that the silver lines have some weimeramer in them.
Anyway, Ive only owned choc labs so Im not plugging this from a black lab bias.
This theory all stems from the FACT that the within the labrador geneology the gene pool is much smaller on the choc/yellow side vs the black lab side. What this means is that you run a higher risk of inbreeding and/or having to overlook some traits when line breeding for the choc or yellow color. This was much more of a problem 20 years ago than it is today. As such you MAY see a lower level of hunting desire in these two colors vs a black dog, since they are more often breed for color/looks first rather than hunting ability.
Whats this all mean? Actually not much. Research the breeding of the dog your going to get... if you care. Some people dont. If you, do look for black factored choc or yellows. Meaning one or both the parents where black or were produced from blks. Today its not uncommon to find two blk that produce black yellow and choc pups in the same litter. Another thing. Its also usually a good idea to see kind of breedings been taking place in the linage i.e hunt tests, field trials or more show lines. The hunt lines are likly to produce a pup with a stronger hunt desire vs a dog that has been repeditly chosen for looks. Not always the case, but the odds are in favor of it. Most any dog will retrieve and can be trained to retrieve. However a dog with a linage full of senior hunters or trial champs indicates selective breeding for certain traits such as trainability and desire to retrieve. If im going to spend 700-1000 on a puppy I want to stack the odds in my favor.
Personally I look for parents, grandparents to be at least a JR hunter (senior prefered) with a strong hunt test/field trial showing in earlier breedings. I like a little field trial blood in there but not much and preferably back in the grandparents or later. I think trial dogs are too hyper at least for my style of hunting.
i second the genetic disorder testing criteria mentioned above. Anyone breeding dogs today who doesnt do this is a criminal
....its like taking x-lax when you have a bad cough. It wont clear up your lungs, but it sure stops you from coughing