You can get a paint camera to get the formula for a color… however, its just going to tell you the factory paint code… and im sure your neighbor is not the only one with that same color / model… although if it comes up, then you know it is his. I would take a pic of his car and your car where the damage is, you usually can piece it together by where the damage is on his car and your car.
He should admit to it, as its ovious… but I have never heard of a lab to test paint… and even if there is, im sure its going to cost you more money to get the test done than to fix the car… if not it would be close im assuming.
Just ask him man to man, and if he cannot admit it… call one of your friends from the local PD