Does camouflage really helps in modern air combat? Aircrafts engage each other mostly on beyond visual range distances, and dogfighting in kinda rare now. Also, HUDs should assist in tracking of targets and highlight them, so camo will make no difference. The only use for camo I can think of is to hide the aircraft while it's stationed on the airstrip - in a relatively vulnerable position.
My guess is that most of the camouflage is to hide the airplane from humans on the ground. I would also guess an airplane providing support for ground troops would likely get shot at. They would paint a fake canopy on the underside of the Warthog: http://www.flickr.com/photos/arnielee/4105880397/ . This was to make it hard to tell which way the airplane was turning.
> They would paint a fake canopy on the underside of the Warthog
I'd just hate that someone painted my exact location on the bottom of my plane so the enemy knows exactly where I'm sitting so they know exactly where to shoot at. I mean I'm sure everyone would know where the pilot is, but this would be like the Imperials painting a massive bullseye target around the ventilation tube on the Death Star.