{$modeswitch objectivec2}
     
    interface
     
    uses
      CocoaAll,
      ...;

    const
      NSWindowTitleVisible = 0;
      NSWindowTitleHidden = 1;
     
    type
      NSWindowTitleVisibility = NSInteger;
     
      NSWindowGlam = objccategory external (NSWindow)
        function titleVisibility: NSWindowTitleVisibility; message 'titleVisibility';
        procedure setTitleVisibility(AVisibility: NSWindowTitleVisibility); message 'setTitleVisibility:';
        function titlebarAppearsTransparent: Boolean; message 'titlebarAppearsTransparent';
        procedure setTitlebarAppearsTransparent(AFlag: Boolean); message 'setTitlebarAppearsTransparent:';
      end;
     
    { TForm1 }
     
    procedure TForm1.FormShow(Sender: TObject);
    var
      w :NSWindow;
    begin
      w := NSView(Self.Handle).window;
      w.setTitlebarAppearsTransparent(true);
      w.setTitleVisibility( NSWindowTitleHidden);
     
      w.setBackgroundColor( NSColor.greenColor ); // <-- not required, and can changed to any color
   
    ...

    end;