Those uniforms look confederate.
Prior to the Civil War, being the cheapest color, gray was used for the uniforms of state militias in both the north and the south. For the same reason it was used in West Point. When the war started, their forces being composed entirely of state militias, the south used gray. The north, on the other hand, had regular federal troops in blue. Initially their state militia forces were also often in pre-war gray uniforms but they switched to union blue to distinguish themselves from the south. West Point, however, has continued to use its pre-Civil War gray uniforms to this day.