code: function () {
                      var rgb;
  
                      if (parserInput.currentChar() === '#' && (rgb = parserInput.$re(/^#([A-Fa-f0-9]{8}|[A-Fa-f0-9]{6}|[A-Fa-f0-9]{3,4})/))) {
                          return new(tree.Color)(rgb[1], undefined, rgb[0]);
                      }
                  }
docs: A Hexadecimal color  #4F3C2F  `rgb` and `hsl` colors are parsed through the `entities.call` parser.