Those are correct Jim. Just to add, the collars would have probably been taller than found later in the war, more like those on Mexican War uniforms. The gray color would probably have been a little darker than found on later uniforms.

If you are considering having a uniform made, the buttons would have been the Mississippi "star" buttons....with the initial of the branch in the center of the star and "Mississippi" around the perimeter of the button. If the red is too weird for you, black was the next trim color for Mississippi infantry.

I wish I knew how many (how few) units actually wore uniforms prescribed by the 1861 Mississippi legislature.