Wearing the wrong color to a battle

From Shelby Foote’s The Civil War: Fort Sumter to Perryville (337, 347):

[At the Battle of Shiloh, also known as the Battle of Pittsburg Landing,] The Orleans Guard battalion, the elite organization with Beauregard’s name on its muster roll, came into battle wearing dress-blue uniforms, which drew the fire of the Confederates they were marching to support. Promptly they returned the volley, and when a horrified staff officer came galloping up to tell them they were shooting at their friends: “I know it,” the Creole colonel replied. “But dammit, sir, we fire on everybody who fires on us!”

[A day later, Beauregard] received a shock … He noticed in some woods along his front a body of troops dressed in what appeared to be shiny white silk uniforms. At first he thought they were Federals who had breached his line … Presently, though, a staff officer, sent to investigate, returned with the explanation. There were the general’s own Orleans Guard battalion, who had turned their dress blue jackets wrong side out to put an end to be being fired on by their friends. Yesterday they had startled the defenders of the Hornets Nest by charging thus with the while silk linings of their coats exposed; “graveyard clothes,” the Federals had called them.