Using genetic testing to establish the gender of an animal is pretty easy, as sex chromosomes are distinguishable from the rest of an animals chromosomes.

Using genetic testing to identify hets would be rather costly, simply because (as far as i know) the genes responsible for specific color mutations are not identified. That means in order to find out if your animal was het you would first need to determine specifically what genes were responsible for producing whatever phenotype you were looking for. This alone would be quite costly im sure.

Maybe once ball pythons are sequenced, genetic testing might be viable though. Its quite amazing how technology in this feild is exploding (with DNA barcoding and whatnot) so maybe we will see this becoming viable within the next few decades

By the way i am no master of genetics or anything so if somebody sees something wrong with my reasoning feel free to point it out ;P.

-Dylan