I'm not sure it's a wise decision purchasing from amish breeders? but that's up to you.
I honestly have never heard the reasoning that the color right after birth is more of their adult color especially with sables.
Sables are ever changing, even mine at 5 years of age has darkened up more than she was just last year
You might get a better idea of what it would end up by seeing both parents.
I guess my question to you is, if you pick one, and end up with a light sable is that going to make a difference?
We all have our color preferences, but I would be more concerned that the parents of these puppies are at the very least, hip/elbow certified??