Who were the Blues and who were the Grays during the American War?

During the American Civil War (1861-1865), the "Blues" referred to the Union forces, who wore blue uniforms, while the "Grays" represented the Confederate forces, clad in gray. The conflict arose primarily over issues related to slavery and states' rights, with the Union fighting to preserve the United States and the Confederacy seeking independence. The war resulted in significant loss of life and profound social and political changes in the nation.