This is the beggining of your file already changed to forum background (#078FB9, a kind of blue)
/*
PrestaShop CSS
Theme et-clean-blue
modified/designed by Static
www.ezytrader.com
Description
Nice cleaner/lighter blue version of the default theme shipped with Prestashop
Simply adjusted layout of header, removed some block images and replaced with background color, added background color for footer, lightened existing block graphics and background colors and replaced pink block graphics to blue.
*/
* {
padding:0;
margin:0;
}
body {
background-color: #078FB9;
font-size: 11px;
font-family: Verdana, Arial, Helvetica, Sans-Serif;
color: #5d717e;
text-align:center;
}