There is no "correct" formulae for Confederate uniforms. The grays were produced by using natural pigments and faded accordingly. Gray was by no means the sole color; homemade garments were relied upon to a great extent and at home the cloth was dyed with copperas, walnut shells, dirt, rust, anything that gave a semblance of color to the cloth--resulting in a variety of shades of brown and tan. Imported uniforms from the UK were a darker gray in general. First person accounts of their clothing frequently mentions "greenish gray". The infantry soldier you are painting could have had just about any shade of gray or brown in his clothing. Buttons are a consideration also, and ranged from regulation brass to pewter and wood. Regs called for colored facings-collar and cuffs-- in the same colors used by the US, that being yellow for cav, red for arty, light to medium blue for infantry. Ash and trash also the same. The thing about those colors is that the quartermaster was hard pressed for ANY cloth for uniforms and often, though not always, it proved impossible to provide the facing colors. Also individual units faced jackets with their own idea of what was good for them, black being popular. So you can use colored facings but it is not necessary nor even common. Remember shirts and socks were private acquisitions too so they can be any color and if that figure has an exposed shirt (I don't remember) it can provide a little color in the otherwise drab uniform. Use browns and grays Jason and you cannot be wrong in your choices.