Header Background Color In Avenue

Site URL: http://www.mvcchurch.org

I'm interested in adding an infinite width header to my site in the Avenue Template.  It doesn't look like there an out of the box way to do this, but is there a way to code it that is consistent with the height of the current header and menus? website is www.mvcchurch.org

Thanks!

Add to Home > Design > Custom CSS

#canvas {
    max-width: 100% !important;
}
#header {
    margin: -85px -75px;
    padding: 10px 75px !important;
    background: gray;
}