The menu in the Delicacy theme consists of several layers of CSS borders, background colors and gradients. You can center the menu using the following CSS, but it messes with the menu color gradients. Paste this into your Appearance → Custom Design → CSS editor and click the Preview button to see what I mean:
#navigation > .main-menu {
text-align: center;
height: 48px;
}
#navigation > .main-menu > ul {
float: none;
width: auto;
}
This will work to update the colors back to something more reasonable. Note that I made the colors a little darker because I thought it looked better but you can adjust the color codes to your liking:
#navigation {
background: #5E164D;
border-bottom: 1px solid #731b5f;
}
#navigation > .main-menu {
background-color: transparent;
background: -moz-linear-gradient(top,transparent 0%,rgba(0, 0, 0, 0.3) 100%);
background: -webkit-gradient(linear,left top,left bottom,color-stop(0%,transparent),color-stop(100%,rgba(0, 0, 0, 0.3)));
background-image: -webkit-linear-gradient(top,transparent 0%,rgba(0, 0, 0, 0.3) 100%);
background: -o-linear-gradient(top,transparent 0%,rgba(0, 0, 0, 0.3) 100%);
background: -ms-linear-gradient(top,transparent 0%,rgba(0, 0, 0, 0.3) 100%);
background: linear-gradient(to bottom,transparent 0%,rgba(0, 0, 0, 0.3) 100%);
filter: progid:DXImageTransform.Microsoft.gradient(startColorstr='#731b5f',endColorstr='#5E164D',GradientType=0);
position: relative;
}
#navigation > .main-menu > ul {
background: none;
filter: none;
}
#navigation::before, #navigation::after {
background: none;
box-shadow: none;
}
Because of the complexity of the layers of stuff in that menu, you may need to do a bit more experimenting to get it looking how you want.