Change background color of "head telephone number extra info"-area in the top

phone info has its own class – so why not use it:

.phone-info {
    background-color: blue;
    padding: 5px 10px;
}

Depends on your settings you had to set for transparency header too:

#top .av_header_transparency .phone-info {
    background-color: blue;
    padding: 5px 10px;
}

The font color is set via:

.header_color .phone-info a {
    color: red;
}