Thyer,
Great job on the painting, these look really good.
One thing you mentioned was "... I guess historically the 'butternut' rebel was most common?" Well, no. Despite popular opinion and Hollywood, brown uniforms on Rebs were not as common as gray. Was "brown" clothing used? Sure it was, but most government issue clothing started out some shade of gray. Oxidation of some the natural dyes used, dirt, dust, smoke, etc might give the appearance of a light brown shade over time, but generally the clothing would appear some sort of gray. By the summer of 1863, for example, the Richmond QM Depot was issuing jackets made of a dark-blue gray English wool cloth ("Army cloth") brought in through the blockade. These jackets were issued until the end of the war, along ones made of cloth from Southern mills.
Rebs were ragged at times on campaign, but the soldiers did get issued new clothing. For example, most of Longstreet's Corps was issued new uniforms in Virginia prior to the move to Chickamauga. A South Carolina officer in Kershaw's Brigade described their uniform as "dark blue jackets and light blue trousers." These were made of the English cloth.
If you are interested, I would recommend that you take a look at the Time-Life Echoes of Glory series, which will give you a good overview of original uniforms, weapons and equipment for CS and US soldiers. Also, Don Troiani paintings are a good guide, as he pays attention to the details, and doesn't let "artistic license" get out of hand. Much of his work has been printed in several books that are available most places.
When you get a chance, I too would like to see a photo of the CTS figures with some Conte troops.
Thanks,
Oddball