Deciding what color to paint aircraft has always been a contentious issue. Many different color schemes have been tried over the years. At one point, the U.S. Air Force ran some extensive tests and concluded the color that best hid an aircraft in flight was a shade of pink. The results of this effort were never implemented by the U.S. Air Force. But other countries have deployed aircraft (and ships) painted in various shades of pink. Of it's called "salmon." It's still pink, and it actually works.
During the Iraq war, army and marine helicopters were all over the place, and troops had plenty of opportunity to see both types together. You could easily tell them apart. The army choppers are painted dark green while the marine helicopters are painted "Haze Gray" One thing everyone noted was that the marine helicopters were always harder to see. If a marine and army helicopter were flying close together and approached you from a distance, you would always be able to pick out the army chopper first. The marines changed the color of their helicopters after the Cold War ended, when they realized that their most likely opponents would be looking up at them, not down from the sky. For protection from enemy aircraft above, a green paint job gives you more protection. But from below, a gray paint scheme works better to hide you.