Hi @pslovetye,
Try adding following CSS code in your site using any of the following plugin.
Change the background color in the code to whatever you want to use.
#footer-sidebar div {
float: right;
width: 320px;
margin: 0 10px;
background-color: #ddd;
}
http://wordpress.org/plugins/my-custom-css
http://wordpress.org/plugins/simple-custom-css
Best Regards,