The honor of escorting a regiment's colors was given to individuals selected from the companies of the regiment as the color bearers and color guard. The color bearers were usually sergeants and the color guard were corporals. This select squad was placed in the ranks on the left of the color company, and the color company was placed just to the right of the regiment’s center when it was in a line of battle. This arrangement placed the colors at the regiment’s center. The color squad was composed of a national color bearer and a regimental color bearer with seven color guards. If the regiment had only one color, the color squad would consist of a bearer and eight guards. The color guard was a target of enemy fire and it took brave men to volunteer for this job. Capturing the colors was a battle trophy: loosing your colors was a dishonor. The casualties in the guard were always high. When the bearer was unable to go on, another member of the guard would move forward to rescue the flag. The flag of the regiment served as a rallying point for the men and often indicated the location of its leaders. The flag and its bearer usually lead the regiment into battle, therefore offering themselves as the first targets to the enemy. You can see pictures of Maine regimental colors at the state archives here.
       The 3rd Maine color guard company, Company K, is made up of volunteers from the ranks of the infantry and forms at need to perform special functions. These are:

• To honor and remember the color guard of the 3rd Maine who served at Gettysburg
• To honor and present the Flag(s) of the 3rd Maine at parades and ceremonies
• To store, maintain, and transport the Flag(s) to events
• To form at the pleasure of the captain of Co. A at other events such as living
  history presentations or battle reenactments
• During winter encampment to tell the story of the Flag(s) in the Civil War for schools, historical societies, and other interested groups