They came in a number styles, depending on the depot which issued them and the period of the war.
Jackets are available either unlined or with an onaburg, linen or cotton lining.
Many reenactors prefer lined jackets since the lining wicks persperation and actually results in more comfort in hot weather - believe it or not. Research seems to indicate that the initial uniform for the 3rd Georgia regiment included a shell jacket in mixed gray wool with black trim on the collar and cuffs. However, by mid-war this militia style look is very likely to have faded into a hodgepodge of different styles and colors, dependent only on whatever happened to be available to the soldier when his first uniform wore out. Jarnagin shell jackets are quite good, although the very discerning reenactor may prefer to make his own jacket from a kit, using more authentic reproduction fabrics and handsewing all visible seams. If you are not particularly good with a needle, you can hire someone to assemble the kit for an additional fee, resulting in a garmet approaching double the price of the middle-ground mail order equivalent.