Open inc/functions.php and around line 1684 (or so)
Find:
$template .= "<div style='position: fixed; bottom: 0; left: 0; color: white; font-size: 10px; width: 380px; '>A total of {$GLOBALS['numberofqueries']} queries were used in this page. They were: {$GLOBALS['queries']}</div>";
Replace:
color: white; with what ever you want.
To remove it all together just erase the whole div so it looks like this:
$template .= "";