I don't use php so I'm probably barking up the wrong tree, but couldn't you have each side menu as a different div, then you can set specifics for that div eg.
div#lefmenu a:hover {border-color: rgb(30%,30%,60%);}
div#rightmenu a:hover {border-color: rgb(50%,50%,60%);}
Obviously changing these colours for what you want. If this isn't what you want perhaps you can link to the site.....
HTH,
[edit] looks like I was beaten to it by two mins - damn