Yes, Ian, the Union (northern) forces wore blue while the Confederate (southern) forces wore gray. But there was little else different in their uniforms. Most senior Confederate officers had been officers in the Union army prior to secession and adopted that army's garb whole-cloth as standard issue for their new commands, with the minor alteration of changing the predominant color from blue to gray. With a good coat of dust on their uniforms they surely had difficulty telling each other apart.