Yes it's a codominant/incomplete dominant (or possibly dominant) mutation, and yes it's also heterozygous for that mutation (there are no homozygous deserts)
Yeah I think he's thinking of desert ghost...which is recessive. And those hets are worth every penny!
Other species: 1.0.3 pacman frogs (sunkissed, super apricot, super blue, super lime green); 0.2 crested gecko; 1.0 hypo hog island boa; 0.1 normal boa; 1.0 rottweiler; 1.0 chihuahua