Once more, the U.S. Army is following the lead of its troops, and allowing them to apply camouflage to their weapons (which tend to be uniformly black, and standout next to camouflage uniforms.) Unit commanders are authorized to allow their troops to paint a camouflage pattern on their weapons. For years, troops have been doing this with special camouflage tape, which could be removed to get back to "regulation" black for inspections. This was done with the tacit approval of unit commanders. But as far as the senior commanders were concerned, this was unauthorized behavior. All of this is nothing new, it's part of an old custom.
For over a century now, infantrymen has sought to find new ways to hide themselves on the battlefield. Even before World War I, brightly colored uniforms gave way to ones (green or tan) that better blended into the background. During World War II, camouflage pattern uniforms, and face paint, began to appear.
In the last decade, troops have been taking this movement the last mile. A good example of this is the effort to camouflage those items that are still black, or some other metallic color. This is sometimes done with paint, even if commanders disapprove. More often, troops used camouflage colored tape. This stuff, however, has to be removed from metal or wood items after a soaking (otherwise rust or rot will set in). Despite that, the tape has many other advantages. It comes in different colors, so when the troops go from forest areas, to deserts to snowy climates, they can continue to camo their weapons and equipment. The tape also makes the equipment quieter (less clanking) and less slippery in the rain. For all these reasons, troops have been particularly eager to put a camo look on their weapons and increasing array of electronic gear.