You're correct that there isn't a "sunglow" gene. I wouldn't call it random, maybe pseudo-random. Like I said, two sunglows will throw a lot more sunglow babies than two regular amels. But it was a selectively bred trait. i.e. the most vibrant babies were bred together, then the most vibrant babies from that were bred together, etc.
They're allelic to each other with motley being dominant to stripe. So stripe is its own distinct allele and a single gene causes it. Even though they originated out of motleys, they're not selectively bred.Since we're talking about genetics, stripes/motley is the same kind of thing, right? I was under the impression that stripe is just a very selectively bred form of motley?
Also, interesting change Jake has gone through. As a juvenile I wouldn't have called him sunglow (though maybe the camera is playing tricks), but as an adult he definitely makes the cut IMO.