I guess I am having trouble imagining if, when or where I would wear purple pants! So the color of the shoes just can't get to the front of my mind. But I would have to speculate dark.....say cordovan or black.
Of course, when I was your age I was wearing gaudily painted platform shoes, bell bottom trousers or embroidered jeans, plastic "Nik Nik" shirts, and carried an angel food cake cutter in my back pocket to comb my 'fro on weekends and still wore bespoke HK suits to work during the week. So I suppose that I can see the reason for the different styles.