@ Diplodactyla There are lots of differences(you named one color, well price too LOL) One of the major differences being size, female N.amyae can reach weights over 75g and males in excess of 30g, N.asper only get a little above 30g for a female and around 18g for a male.
Also their range in Australia is considerably different as well. Throw N.sheai into the mix and there are even more differences to sort out. Which is why they were separated from the original blanket of N.asper which used to cover N.amyae, N,sheai, and N.asper.
N.asper also has much a more narrow head and not as pronounced jaw line as amyae do. They are also worlds apart as far as temperament. amyae are more aggressive, willing to hold their ground, and asper tend to be more flighty more apt to run and hide.
