[MarkFL]

The stylevar that controls the background color of that element is named "sidebar_background" but that stylevar controls more than just that element.

If you wish to change the color of just that element, one way to do that is to open the template named "userprofile.css" and locate the selector that reads:

#sidebar_container.member_summary 
{
	color: {vb:raw moduleinactive_text_color};
	background-color: {vb:raw moduleinactive_background_color};
	background-image: {vb:raw moduleinactive_background_image};
	background-repeat: {vb:raw moduleinactive_background_repeat};
	border-color: {vb:raw moduleinactive_border};
}

And change the "background-color" attribute to your liking.