Years ago, the cam experts fitted a tank with lightbulbs and stuck it on the horizon in normal daylight. When the lights were switched on the thing damn near disappeared!
It seems that if a light system could be made lightweight enough to be fitted to aircraft, it could be a very effective daytime [obviously, stupid!] camouflage... Mind you, you'd have to remove the fuses before night ops - or handcuff the co-pilot's hands to his ankles!
After the first week of the first Red Flag, the American crews told the Vulcan operators that the standard European cam was still pretty effective, even against the desert background; but as soon as the white underside was exposed during maneouvre, the thing could be spotted from miles away. That caused the 'wrap round' camouflage scheme that appeared on the Vulcans soon after. Disruption of regular shape appears to be the most effective cam, as seen on some of the more whacky zig-zag paint jobs of a lot of warships during WWII.