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 I've tried various Gamma settings including the PoserPro2010 Gamma 1 setting- as well as gamma 1.5, and 2.2. I do see changes in skin tone- but the grey graphite eyebrows remain

I had the same problem with another vendor's textures.  In the textures the alternate specular input channel was connected to the bump map instead of a true specular map.  If this is the case with Rio's textures, check out page 76 of this thread.  On this page Bagginsbill shows us how to change the VSS skin shader so it directly uses the color map.  The grey eyebrow effect should go away.