I'm by no mean an expert on boas but Imo you may be onto a line bred trait for color or pattern. Everyone has said they see nic or CA influence and I completely agree but selective breeding gets selective offspring. They are very nice looking and I would keep selectively breeding to try and get more and more extreme examples of the purple. Who knows maybe you will be able to name your own line of boa morph sorta like all the pastel lines out there. He's a link that may help you in the future. It won't help this situation but if you want to get more into the genetics of boas and breeding it will be a huge help. Just keep in mind morphs and localities are completely two different things.

Boa calculator:

http://www.owalreptiles.com/boagenetics.php