title: Imagemagick: how do I an irregular region of color
body: <p>When I have an image like the following, is it possible to convert the outer (!) orange to transparency? It's like trim, but I need to remove the outer region of orange color and convert that color to transparent. However, the inner orange must not be touched.</p>
  
  <p><a href="https://i.stack.imgur.com/Zx5HL.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Zx5HL.png" alt="enter image description here"></a></p>