You’ll need to modify the CSS code — the menu background is an image set in this CSS:
.main_nav ul, .main_nav {
background: url("../images/grey_menu_bg.png") repeat-x scroll center top transparent;
border-bottom: 1px solid #DDDDDD;
float: left;
height: 49px;
list-style: none outside none;
margin: auto;
width: 960px;
z-index: 999;
}
The font color is set here:
.main_nav ul li a, .main_nav li a {
border-left: 1px solid #DDDDDD;
border-right: 1px solid #FFFFFF;
color: #404040;
display: block;
float: left;
font-family: 'Gnuolane';
font-size: 16px;
margin: 0;
padding: 13px 25px 12px;
text-transform: uppercase;
}
But as you are using a Commercial theme, you should look to the vendor for support if you need further assistance with it.