Prior to the Civil War, each unit in the military distinguished themselves from others by the style and color of their clothing. The Civil War started out that way, but it was soon recognized that distinguishing enemy from friendly was difficult without "uniform" clothing. While the Confederates adopted gray, Union soldiers were dressed in blue.

Some regiments adopted symbols as ways to carve out their particular unit from others. Early on these symbols were color coded to help distinguish divisions. Red was for 1st Division of Corps, white for 2nd, and blue for 3rd. Additional separation identifiers were added as the armed forces grew and became more specialized. For the 4th Division of the VI, IX, and XX Corps the color green was chosen. For the 4th Division of the XV Corps, yellow was chosen. Orange was used for the 5th Division. For administration or headquarters there were badges made with several colors.

Not all units chose this method, or at least not all knew about the new idea. The U S Army Field Manual version FM 21-13 published in August 1961 asserts that General Philip Kearney ordered his men of the 3rd Division to wear a patch in the shape of a red diamond on their hats so they would be distinguished from other troops.