public RenderingSettings GetFirstRenderingSettings(Document document)
{
    // RenderingSettings isn't used to support family document.
    if (document.IsFamilyDocument)
        return null;

    // Get 3d view
    List<View3D> theView3Ds = new List<View3D>();
    foreach (View3D view3D in RetrieveElementByType<View3D>(document))
    {
        // It's strongly recommend to get  RenderingSettings from visible 3d view, 
        // although it can retrieve data from an invisible one,
        if (view3D.IsTemplate || !view3D.CanBePrinted)
            continue;
        return view3D.GetRenderingSettings();
    }
    return null;
}

public static List<T> RetrieveElementByType<T>(Document document) where T : Autodesk.Revit.DB.Element
{
    FilteredElementCollector collector = new FilteredElementCollector(document);
    return collector.OfClass(typeof(T)).Cast<T>().ToList<T>();
}

Public Function GetFirstRenderingSettings(document As Document) As RenderingSettings
   ' RenderingSettings isn't used to support family document.
   If document.IsFamilyDocument Then
      Return Nothing
   End If

   ' Get 3d view
   Dim theView3Ds As New List(Of View3D)()
   For Each view3D As View3D In RetrieveElementByType(Of View3D)(document)
      ' It's strongly recommend to get  RenderingSettings from visible 3d view, 
      ' although it can retrieve data from an invisible one,
      If view3D.IsTemplate OrElse Not view3D.CanBePrinted Then
         Continue For
      End If
      Return view3D.GetRenderingSettings()
   Next
   Return Nothing
End Function

Public Shared Function RetrieveElementByType(Of T As Autodesk.Revit.DB.Element)(document As Document) As List(Of T)
   Dim collector As New FilteredElementCollector(document)
   Return collector.OfClass(GetType(T)).Cast(Of T)().ToList()
End Function