You can change the background-color using a:hover:
<style type="text/css">
#mylayer a {
padding:5em;
background-color:#CC0000;
}
#mylayer a:hover {
background-color:#CCCCCC;
}
</style>
</head>
<body>
<div id="mylayer">
<a href="#">mylayer text</a>
</div>
</body>
ben