Wouldn't a marker defeat the defintion of a recessive trait? If there were in fact visual markers that could reliably prove the possession of a recessive trait, wouldn't the recessive trait i.e. albino or pied then become a Co-Dominate trait. Breed two pied's with markers together (asuming they are both 100% het), you get a pied, 2 66's and a normal, statistically. Lines right up with what would happen if you were to breed highly visible Co-Dom's i.e. mojave or pastel. All in all, probably seriously de-valueing the recessive trait snakes.
I have a friend who just bred 2 het for albino BP's, and got the textbook clutch, 1 albino, and 3 normal looking snakes. 2 of the 3 are brighter in color than the other, and he's assuming that those are the 2 het's, but in reality it may be none of them are het, or all 3 of them are het. The only real way to prove is to breed.
It also pains me that breeders sell there PH's for considerably more than normal, but some of these folks are selling 50% PH pieds for over a 100 bucks. Suckers are paying these prices, aw man.