Yes, it is genetic. Here is an excerpt from the link above for those who don't feel like clicking on it:
"Experts say that largemouth bass with the coloration are incredibly rare---so rare that that researchers have only seen one confirmed case in Florida since the 1980s. What gives this normally olive-green or gray fish such a bright orange sheen? According to researchers, it may be due to a genetic anomaly called xanthism. Also known as xanthochromism, this genetic condition causes unusually yellow or orange pigmentation in animals, similar to how albinism causes a lack of pigment. The condition is especially common in birds, and certain species---like parrots---are deliberately bred for the trait. Sometimes xanthism can also be caused by an abnormal diet. "To put its rarity into perspective, our Freshwater Fisheries Research Long-Term Monitoring Program has sampled 255,632 largemouth bass from 175 different water bodies over a 10-year period and have no reported sightings of this genetic phenomenon," researchers wrote. "In fact, the only sighting our freshwater fisheries researchers have of these orange bass is one photo from an electrofishing trip nearly 30 years ago." Researchers did not specify what happened to Puckett's rare catch, but those close to the angler claimed it was released. In any event, catching such a fish is truly a once-in-a-lifetime experience."
