Olive drab

Olive Drab was the color of the standard fighting uniform for U.S. GIs and tanks during World War II. U.S. soldiers often referred to their uniforms as "OD's" due to the color. There are very few countries, if any, that still issue Olive Drab uniforms.

As a solid color, it is not as effective for camouflage as multiple-color camo schemes(i.e. US Army Combat Uniform, tigerstripe, MARPAT, Multicam, etc.), though it is still used by the U.S. military to color off-duty uniforms.