The most formal of a Marine's uniforms outside of the elaborate evening dress uniforms of officers and senior enlisted, it is often referred to as "Dress Blues", due to its color (as distinguished from the green and khaki service uniforms), and can be worn in many forms. It is the only uniform of the United States military to use all of the colors of the nation's flag and incorporates button designs which are the oldest military insignia still in use in the United States Armed Forces to this day.