Evidence for uniforms worn by a specific command like this would have to come from first-hand testimony. Accounts written by officers and men of the command should prove useful, as would reports of anyone who saw the company before leaving for Virginia. Accounts published in Atlanta newspapers during the spring of 1861 should provide details about volunteers from Fulton County.

Based on service records of officers, it appears that the company organized on May 14, 1861, officers receiving commissions on June 14th. Payments date from Aug. 2, 1861, so that must be when the company was accepted in Confederate service. In 1860 Capt. Frank M. Johnston, Lieut. Wm. T. Mead and Lieut. Frank M. Stovall had been clerks working in Atlanta business offices; Lieut. William Mackie had been a sign painter in Dekalb County.

Special uniforms worn by individual companies date from the antebellum period. Because the new government did not have a regularly organized quartermaster department, initially volunteers were given an allowance from which to purchase clothing. The more elaborate militia uniforms disappeared almost as quickly as they wore out in the field. These were often replaced with whatever officers and men could acquire, which included hand-made clothing from home. At any rate, you would not have seen Georgians dressed in green at Gaines Mill or Gettysburg.

Along those lines, Capt. Johnston's service file includes a receipt for 2-1/4 yards of gray cloth that he purchased on Nov. 21, 1861. He also requistioned two wall tents and six bells tents about two weeks earlier.

Cadet Gray and Butternut Brown: Notes on Confederate Uniforms by Thomas M. Arliskas (2006) should be a useful guide for you.