MediaWiki:Foreground.css

nav.top-bar,
.top-bar.expanded .title-area {
    background: #333333;
}

#navwrapper {
    background: #333333;
}

ul#top-bar-left li,
ul#top-bar-left li a
 {
    background: #333333;
}

ul#top-bar-right li,
ul#top-bar-right li a {
    background: #333333;
}

ul#top-bar-left li:hover,
ul#top-bar-left li a:hover,
ul#top-bar-right li:hover:not(.has-form),
ul#top-bar-right li a:hover {
    background: #000;
    color: #0099cc;
}
.top-bar-section .has-dropdown > a:hover:after {
    border-color: #fff transparent transparent transparent;
}
.top-bar-section .has-dropdown > a:hover:after {
    border-color: #333 transparent transparent transparent;
}