  ColorValue ColorFactor() const {
    return {
        {// this agregate intialize the std::array object, and uses C++11 RVO.
         number_array[0], number_array[1], number_array[2],
         (number_array.size() > 3 ? number_array[3] : 1.0)}};
  }
  ColorValue ColorFactor() const {
    return {
        { 
         number_array[0], number_array[1], number_array[2],
         (number_array.size() > 3 ? number_array[3] : 1.0)}};
  }