code: function () {
                      var k;
  
                      if (k = $(/^[_A-Za-z-][_A-Za-z0-9-]*/)) {
                          if (tree.colors.hasOwnProperty(k)) {
                              // detect named color
                              return new(tree.Color)(tree.colors[k].slice(1));
                          } else {
                              return new(tree.Keyword)(k);
                          }
                      }
                  }
docs: A catch-all word, such as:  black border-collapse