This option is available for DXF, SVG and Report output types and will allows a color selection for the lines representing perimeter, cutouts, insets and labels. Expanding Colors will show the following:

The SVG and Report exports have an additional option, Fill Faces.  When selected the faces will be filled with their corresponing selected color.  Use it to highlight features like insets, cutouts or top face (perimeter) or to create something fun.