You'll have to wait until they're grown, but assuming they're "purebred" it should be pretty easy to tell between those locales. I'd try to describe, after being in the panther community for a while you just sort of can tell right away. I'll try to help though and then I'll link you to some pictures.
Ambanjas primarily come with a background that's teal-ish, and the bars can be red, blue, or even purple. One defining characteristic that many people look for to ID an Ambanja is a highly formed. uhm. headpiece? The word is escaping me right now, but the piece that comes off the nose of panther chameleons tends to be larger in Ambanjas.
red/purple bar-
http://www.pardalis.be/Images/ambanja/ambanja003.jpg
blue bar-
http://www.pardalis.be/Images/ambanja/ambanja007.jpg
Nosy bes can be easier to recognize, they're known for their blue coloration. Now, it depends on whether yours is CB or WC, because breeders are selectively breeding for the crazy blue coloration, if you want to see some outstanding blue nosy be chameleons check out screameleons.com, they have some of the best ones I've seen. Wild Caught nosy be's won't be as spectacularly blue, most are more teal and many have red flecks across their body. One thing about nosy be's is that they don't seem to usually have as defined stripes as the other locales, they're closer to a solid color.
Here's a more greenish one-
http://www.pardalis.be/Images/nosy be/nosy_be003.jpg
And here's a blue one-
http://www.pardalis.be/Images/nosy be/nosy_be_true_blue001.jpg
I saved the Ambilobes for last because they're probably going to be a lot harder to describe. Aside from either having red or blue bars, they can basically be any color. It seems like it's more common to have a blue bar Ambilobe (which is what my boy was) and the backgrounds can be just about any color, red, orange, yellow, or green are the most common.
I'll simply link you to the entire ambilobe page to look at the pictures.
http://www.pardalis.be/ambilobe.htm
I'll add a few of my boy, too, since his colors were a sort of more common color combination in the Ambilobe world
you can see in the pictures that his bars were always blue and his background was anywhere from green to orange, but he usually had red markings on his face. I would go ahead and guess that if you ever see any orange on your boys it's a very good chance they're ambilobes, and ambilobes seem to be the most popular morph out there simply because of the color possibilities.
Do you know how old your boys are right now? If they're not showing any color I'd be concerned that the store sold them when they were far too young, my boy was showing a lot of blue already when I got him.
I'd also like to point you towards chameleonforums.com, it's a great place!
good luck with your new babies!
