system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do airplanes use green camo instead of blue? Wouldn't it make more sense, since they would be less visible on sky?

Thanks!
gpt
First, look at the purposes of camouflage on aircraft. In past and present years they had three different goals--disguise the aircraft on the ground, Disguise the aircraft in the air, or a scheme to make it difficult to judge an aircraft's distance away, speed, altitude, etc.  Green camo falls into the first category.  

Green camo was common decades ago (WWII for example), In those eras most reconnaissance was still completed by aircraft and bombings were done based on visual recognition--green camo made it difficult to see aircraft on the ground.  Keep in mind that many of the airstrips of the time were simple and there weren't many hangers.  Modern grey camo is the best choice for aircraft today. We don't see blue sky everyday and grey has been found to be the best choice for all weather conditions.  In reality, camo matters far less today in an era of advanced radar, weaponry, and GPS.