I thought the Union side was the one with grey uniform?
Confederate wore a warm tan-gray for much of the early part of the war because of lack lf supplies and dye. Before that, the Confederate Army was mostly irregulars and state militia with their own uniform.
Later, they imported steel blue and red uniforms from overseas.
The Union always fought in deep blue and green. I think the harness across the chest is usually associated with Union, and Confederacy is usually displayed as double buttons.
