There is really good input in the posts above, and I think that your still asking the same question.

Yes most of the pics that you posted of the snakes that you like, will get fairly large, much larger than a BCI (your common petstore RTB)

Like someone pointed out, they vary quite a bit in color, of just "normals".

I would look for maybe a very clean Columbian, so that the contrast is still to your likeing. Just remember that baby boas, have much different color than the adults do.