SU Using "Glass/Clear" as Default Color instead of "Default / White" - What's Happening?

In an effort to clean up my model I have been trying to minimize the number of one off colors and textures. As I’ve been doing this, I noticed that parts of my model that were using the Default color became “clear”. It appears that now, whenever I try to apply the Default material setting, it instead paints with one of my colors - “Glass”.

I tried removing the glass material which did a nice job of resetting every face that was using this in error with the Default white that we all see. But then as I started creating new faces (as seen below) it created those faces once again with one of my glass options.

I assumed there was no way to change the Default material, and I certainly haven’t tried, but any sense for how this is happening?

The glass material is probably applied to one side of the face and likely you have the back face on the outside there. Change your face style to Monochrome to check for and correct exposed back faces. Then you could use something like Material Tools from the EW to remove back face materials. Or maybe it just makes sense to delete all of the In Model materials and start over after you are sure the face orientations are correct throughout the entire model.