wdCalendar generar color aleatorio al crear evento

    $sql = "insert into `jqcalendar` (`subject`, `starttime`, `endtime`, `color` ,`isalldayevent`) values ('"
      .mysql_real_escape_string($sub)."', '"
      .php2MySqlTime(js2PhpTime($st))."', '"
      .php2MySqlTime(js2PhpTime($et))."', '"
	  .mt_rand(1,21)."', '"
      .mysql_real_escape_string($ade)."' )";