[Airchallenged]

Okay I have a Union Manual printed after the war by Gen Emory Upton which changed Hardee's Manual (which was being used by the north but with out his name since he was a southern general) to fit Union standards for the war. Here is what it says about the color guard for a Union Regiment:

It is placed in the same location as a Confederate Guard but is made of seven Cpl and One Sergeant. the Sgt and three senior Cpl in the front rank and rest in the rear. One Cpl to the Sergeant's Right and two to his left. The Sergeant would carry the National Flag and when the Regimental Flag was present it would be carried by a sergeant (I would assume the senior color Cpl promoted) who would take the place of the "center" Cpl. All of the Color Guard was to be selected for "Bravery, and for precision under arms and marching."