My black barathea argyll has interchangeable silver, or, black buttons. I think the understated black buttons look very smart, for the right occasion. How is this done? Where each button goes there is a hole(with stitching round the edge) in the cloth, the button "eye" is passed through the hole from the outside and a very small "key ring" type thing is put on to hold the button in place. Some military tunics have the same facility and in these cases, it is for ease of cleaning the tunic and the buttons.