os << std::ios::hex << "#" << color.red << color.green << color.blue;
os << "#" << std::hex << color.red << color.green << color.blue;
toString(const RGBColor& color){  std::ostringstream os;  if (color.transparent)    os << "transparent";  else    {      os.width(2);      os.fill('0');      os << std::ios::hex << "#" << color.red << color.green << color.blue;    }  return os.str();}