When I show a detail of a 3D object in layout with a detail window, open surfaces are shown as dark and closed are shown as lighter. All geometry is in the default layer, and none of the display settings have been changed. This is occurring in shaded mode. It is okay when I rotate in the detail, but when I click out of the detail the open surfaces turn much darker.
I’ve experienced something similar, and in my case found that the surface normals on the “dark” objects needed to be flipped in order for them to appear unified in the detail view. I’m not sure if that step had any negative consequences or effects on the model, but it did get the drawing out the door on time so…