function DesktopColor(const x,y: integer): TColor;
var
  c:TCanvas;
begin
  c:=TCanvas.create;
  c.handle:=GetWindowDC(GetDesktopWindow);
  result:=getpixel(c.handle,x,y);
  c.free;
end;

function ColorToHTMLHex(Color: TColor): String;
begin
  Result := IntToHex(ColorToRGB(Color), 6);
  Result := Copy(Result, 5, 2) + Copy(Result, 3, 2) + Copy(Result, 1, 2);
end;

procedure TForm1.Timer1Timer(Sender: TObject);
var
  pos: TPoint;
begin
  GetCursorPos(Pos);
  Panel1.Color:=DesktopColor(pos.x, pos.y);
  Panel1.Caption:='$'+ColorToHTMLHex(Panel1.Color);
end;