function get_outline_color()
    {
        if ($this->_props["outline_color"] === "") {
            //see __set and __get, on all assignments clear cache!
            $this->_prop_cache["outline_color"] = null;
            $this->_props["outline_color"] = $this->__get("color");
        }

        return $this->munge_color($this->_props["outline_color"]);
    }