Actually, upon researching the "Reds" flag you were talking about, I think I answered my own question. I came across a website that had an article from 2000 by Howard Michael Madaus. In it, he said that Elliott's Brigade (with whom my 3X GGF in the 22nd GA was attached) fought under a Charleston Depot Flag. He said that by 1865 the Department of South Carolina, Georgia and Florida all fought with a CDF. It was a very informative article.

http://www.confederate-flags.org/confederate%20dept%20of%20south%20carolina.html

Below is a reported example of a Columbus Depot.