Images sized down for post, view image to see at full size.

 

Here is the transmap.

 

 

This is the transmap that came with the material:

 

This is the material room for the skin head material.  This is the edited material with eyebrows removed:

This is the material room for the eyebrow with transparency set and transmap applied:

This is material room for eyebrow with the transparency at 0.  Not that the eyebrow is then a solid color.

I can use an eyebrow brush to paint on new eyebrows (directly to the head material), but that painted on eyebrow doesn't move well when the figures eyebrow is moved, and it means painting a new texture for any eyebrow color change rather than just changing a color in Poser.