code: function(color) { 
          if (color != undefined) {
              this.backgroundColor = color; 
          }
          
          if (this.div != null) {
              this.div.style.backgroundColor = this.backgroundColor;
          }
      }
docs: Method: setBackgroundColor
  Sets the background color of the popup.
  
  Parameters:
  color - {String} the background color.  eg "#FFBBBB"