Gtk2 and Win32.
Color marks for clNone are Not crossed. They must. LCL has code to cross clNone items:
colorbox.pas
if NewColor = clNone then
begin
NewColor := NoneColorColor;
noFill := true;
end
..
Canvas.Brush.Color := NewColor;
Canvas.Pen.Color := clBlack;
..
if noFill then
begin
Canvas.Line(r.Left, r.Top, r.Right-1, r.Bottom-1);
Canvas.Line(r.Left, r.Bottom-1, r.Right-1, r.Top);
end;
Example app: it has ColorListbox and OnCreate event:
procedure TForm1.FormCreate(Sender: TObject);
begin
List.Items.Clear;
List.Items.AddObject('test clNone', TObject(clNone));
List.Items.AddObject('test yellow', TObject(clYellow));
end;
property NoneColorColor set to white.