New fighter jet camouflage schemes 14 years ago
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.