Just going out on a limb but open your system settings and go to the Colors section. Is your box for "Use specified color for shaded with Edges mode" checked? If not try checking it and see if that changes anything. It shouldn't because that is only supposed to be for shaded with edges, but your lines look they would in shaded with edges mode with that box unchecked (linked to the part color).
Go to the Line Format toolbar and deselect the Color Display Mode