Michael did lay it out there with a nice way to put it but I just want to make sure you understand. You had in your last post:
"i can easily understand that explanation. providing it's true, no matter what they are het for, they should produce visible traits in their young."
This isn't true. Both of the parents have to be het for the same trait in order to produce the visible traits. Bulls can be het for quite a few things any more. You could breed animals that are het for axanthic and patternless to an animal that is het for whiteside and hypo and you would get all normal appearing animals possible het for four seperate traits.
So Michaels great explanation is true however you have to know what you are starting with. Thats where your question started I believe is that you didn't know if you snakes were het for anything. I hope this helps. I promise I'm not trying to confuse you!
Shoot me an email if you have more questions. I'm happy to help you out! Take care
Jeremy
Shade Tree Exotics