To change the background of the Site News table go to:
CP » Customize design » Page Editor » Site pages
Code in blue the is code of your background, the image url that is in green is a part of your background so you might want to change it or removed it.
Code located on 29th line
Quote
<table border="0" cellpadding="0" cellspacing="0" width="100%" style="border:1px solid #191E20;"><tr><td style="background:url('/.s/t/961/10.gif') top left no-repeat #5F6C73;padding:15px 35px 15px 35px;">
To change the background of the Site News table with comments go to:
CP » Customize design » Site News » Page with entry full text and its comments
Code in blue the is code of your background, the image url that is in green is a part of your background so you might want to change it or removed it.
Code located on 29th line
Quote
<table border="0" cellpadding="0" cellspacing="0" width="100%" style="border:1px solid #191E20;"><tr><td style="background:url('/.s/t/961/10.gif') top left no-repeat #5F6C73;padding:15px 35px 15px 35px;">