The white color is not accepted by the AKC and the dog would not be eligible to show. The pups are probably registered as "fawns". While white colorations ranging from true albinos, up to cream with a reddish mask can happen from mutations and naturally occurring recessive traits, they are not accepted by the mainstream pug world and are prone to the same problems as other white dogs. Also, because they are being bred for the color variant, there can be inbreeding or close linebreeding which can cause problems of itself. Additionally when the focus of the breeder is color, sometimes they are not paying attention to the breed standards and the dogs lack in quality (as compared to bereed standard).
Most (not all) breeders of non-standard color sports are not getting genetic and other health testing done, so this combined with inherent white dog problems and the dangers of inbreeding would make me steer clear of paying a good deal of money for a white pup....and yes, they are adorable and remarkable.
If a white pug occurred in a litter from a reputable breeder, the puppy would be sold (for less) as a pet quality pup, with a contract to have them spayed or neutered.
In a gentle way, you can shake the world.
- Mohandas Gandhi