It was really hard to get a colorfast green dye in the US for a long time, so the green would quickly fade into a grassy color. Green jackets were the uniform of the US riflemen and sharpshooters from just after the American Revolution to the end of the Civil War. So don't worry about trying to get the green just right!
Out West, where the bulk of the regular Army presence was cavalry, there weren't a whole lot of green uniform tunics in the militia. States mostly bought what was cheap. The whole blue = North/ gray = South wasn't even a hard and fast rule. For the first few battles of the Civil War, there were gray-clad Northerners and blue-clad Southerners, and boy did that confuse the hell out of things.