How use a color mask in Photopaint?

Help!  Using Corel PhotoPaint 2019.

I'm trying to use a color mask to trim off the red part of an object which is around the object's periphery.  Here's an image, As you can see there's a thin red edge all around the periphery of this coin.

 The entire coin is an object.  I use the "picker tool" to select the red periphery (edges) and wish to create a mask so I can remove them.

However, when I use the color mask tool I either get no mask or it selects blotches in the inside of the coin even though I select just the red color picks.

I then go to either regular mode or HSB where I can pick against Hue, Saturation, or Brightness.  I tried selecting "Hue" only which hopefully would just select the red but no luck.   However, nothing I pick can select just those red edges.  Also what does sensitivity against Black or White do?  They seem to do the same thing.

Of course I can't use Magic Wand tool for this as it has a different purpose.

Any help would be appreciated greatly. I never really got adept with masks in Photopaint.