First I airbrushed the mask with an undercoating of violet dye. Then I cut and attached the trim piece with domed rivets. As you can see I made the shape of the trim a bit more interesting than I had originally planned.
Here I have added matching domed rivets all around the surround, purely for decoration.
I then stained the mask brownish black, and left some of the violet (and undyed trim color) showing through to give it more character. Plain old black would have looked bland and modern.