Sticky header

To make the header sticky and change the background color please use this code inside the dedicated area for Custom CSS Code under the Theme Options Panel:

#mainHeader {
    background: none repeat scroll 0 0 #333333;
    position: fixed;
    width: 100%;
    top:0;
    left:0;
    z-index:99999;
}
#pageTitle {
    padding-top:80px;
    margin-top:0;
}
.rev.fullwidth {
    margin-top:-55px;
}

You might need to change the menu text color in order to accommodate the new background and maybe do a little bit of padding.