Background of drop down menu

Hi,

I want to style the background of the navigation, more specific: the menu items with sub menu items as a whole when they are hovered.

You can find the site here: http://specialb.codable.de/

If you hover the menu items which have a sub menu, the sub menu has a blue background and the background of the main menu item still has a white background.

I want to apply a blue background to the whole menu point, a blue background for the main und the sub items as a whole:

<li id="menu-item-206" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-has-children menu-item-206"><a href="http://specialb.codable.de/steuern-steuern/">Steuern steuern<span role="button" class="dropdown-menu-toggle" aria-expanded="false"></span></a>
<ul class="sub-menu">
	<li id="menu-item-1095" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-1095"><a href="http://specialb.codable.de/steuern-steuern/">Überlick</a></li>
	<li id="menu-item-204" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-204"><a href="http://specialb.codable.de/steuern-steuern/buchhaltung/">Buchhaltung</a></li>
	<li id="menu-item-220" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-220"><a href="http://specialb.codable.de/steuern-steuern/lohnbuchhaltung/">Lohnbuchhaltung</a></li>
	<li id="menu-item-231" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-231"><a href="http://specialb.codable.de/steuern-steuern/analysen/">Analysen</a></li>
	<li id="menu-item-239" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-239"><a href="http://specialb.codable.de/steuern-steuern/tools/">Tools</a></li>
</ul>
</li>

On that screenshot the blue frame shows the whole area which should get a blue background when it's hovered.

Is that possible? Which CSS selector, I have to adress?

Thanks for helping me out.