[Nemesis77]

go to your header template.
find

<table bgcolor="{ pagebgcolor}" width="{ tablewidth}" cellpadding="10" cellspacing="0" border="0">
<tr>
  <td>

and Remove it or comment it out by adding
<!-- --> around it.

This will remove the background color you're talking about from your forums home page and most of the site, but there will still be a couple places when view or replying to a thread where it will still be seen.

Newreply template, newpost template, etc.

just do a search for bgcolor="{ pagebgcolor} and remove it or comment it out also.