TColor to HTML color

Put a TColorDialog (ColorDialog1), a TLabel (Label1) and a TButton (Button1) in your form, and assign the Button1.OnClick procedure as follows:

procedure TForm1.Button1Click(Sender: TObject) ;

  function ColorToHtml(DColor:TColor):string;
  var
    tmpRGB : TColorRef;
  begin
    tmpRGB := ColorToRGB(DColor) ;
    Result:=Format('#%.2x%.2x%.2x',
                   [GetRValue(tmpRGB),
                    GetGValue(tmpRGB),
                    GetBValue(tmpRGB)]) ;
  end; {function ColorToHtml}

begin
  if ColorDialog1.Execute then
   Label1.Caption:=ColorToHtml(ColorDialog1.Color) ;
end;