The decision of the United States military to design equipment with its iconic green shade was made during the 19th century. It was during this time that European chemists developed a new type of paint which could rustproof iron. This new creation happened to be green which is why the U.S. military continues to use that particular shade. Technology has long allowed for the advent of rustproofing materials in any color imaginable but because the color originally used works well with camouflage, it is still in use