Well, actually this isn't any sort of secret.
The new animal is the one with it's head on top of the Hypomelanistic corn's head. Kind of a light chocolate color. I believe this may be a new Hypo gene that has been floating around in the Motleys for a long time. I have already hatched out one or two of them in prior years, and as they mature they become very brightly colored hypomelanistic looking animals. I believe this may be the influence that makes many of the Motleys seemingly get lighter colored as they mature.
In your typical Hypomelanism, babies tend to be much brighter than their normal colored siblings. But when they all reach adulthood, it can sometimes be a challenge to tell which ones are actually the Hypos and which ones are just brightly colored normal animals. This particular trait does the opposite. Babies can be easily passed by if you don't pay attention, but will brighten up with every shed.
Of course, this is all just speculation on my part. But I have noticed this brightening effect and it has puzzled me. When I got a couple of babies that looked slightly unusual that hatched out from one of my projects using Motley, I held on to them to see how they would turn out. But we've all been breeding Motleys for quite a long time, and it does puzzle me that if this trait is widespread in the Motleys, then why hasn't anyone else noticed it before?
I have some Caramel Motleys that have gotten so brightly colored that they look every bit as I would expect an Amber Motley to look. When I bred the Milk Snake Phase to the Motley line, I got a few animals that turned extremely brightly colored in the F2 clutches when they matured. In both cases, I can track back the original ancestor of these projects to the original Motley corn I got from Doctor Bechtel. So perhaps it was just the luck of the draw that it hasn't shown up yet in my Lavender Motley project. But I am certainly keeping an eye out for it, now that I know it exists.