Hi James,
Not too sure if you can change this in the template settings or not, but you can easily change this with a little CSS.
In this file - t3-assets/css/css-ef9e3.css
look for:
div.itemListSubCategories {
background: #29304c;
padding-top: 10px;
}
change it to:
div.itemListSubCategories {
background: transparent;
padding-top: 10px;
}
ALSO look for:
#k2Container {
background: #fff;
padding-top: 20px;
}
change it to:
#k2Container {
background: transparent;
padding-top: 20px;
}
Not sure how this will effect the rest of your site, but that's one way, if I understand what you want to do correctly..