Okay, I found out what is happening, which I didn't quite realize.  If you export using "Diffuse" for a texture,  the color will be darkened where ever there is Metalness painted.  You can see the image below for descriptions (Hovering over stuff in 3d Coat often gives you a description).   What seems weird to me, is that changing the Texture Workflow doesn't seem to do anything for me.  "Color (albedo)" seems to get the color information despite being set to "gloss/specular" workflow.
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