I have an almost new one on my 350 four and it's self coloured black plastic - not shiny and not matt, more like satin. The metal bracket is zinc plated and passivated in a dark green shade. The rivets are left natural aluminium if you want it exact. The one for my 400/4 is identical and in very similar condition. The paint you have on now might come off with stripper, but test it on the inside first to see if it changes the surface. If you try any mechanical method of paint removal, it will almost certainly mess up the surface so unless you want to repaint it in satin black, tread carefully.
