background color for widgets

This will make it look very close to the screenshot. Code must be put in Custom CSS plugin.
https://www.ads-software.com/plugins/search.php?q=custom+css

.widget.NextendAccordionMenuWidget {
	background-color: #fafafa;
	border-bottom: 5px solid #bababa;
	margin-left: -26px;
	margin-right: -26px;
	padding-left: 26px;
	padding-right: 26px;
	padding-bottom: 30px;
}

Some additional info, try resize your browser to check and see if the site display things properly in different screenwidths. Also, I think the accordion menu there is kind of pointless since the links are flat, better be using posts and make genres as tag, and use Custom Menu Widget (default) to make links to tag archives.