After clicking the item, the custom class is removed (the color of the item text is changed)
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
<style>
.TopToolbarAlert, .TopToolbarAlert:link, .TopToolbarAlert:visited, .TopToolbarAlert:hover, .TopToolbarAlert:focus, .TopToolbarAlert:active {
/*background-color: red;*/
color: red !important;
}
</style>
</head>
<body>
<form id="form1" runat="server">
<telerik:RadScriptManager ID="RadScriptManager1" runat="server" />
<div>
<telerik:RadMenu runat="server" ID="toolBarMenu">
<Items>
<telerik:RadMenuItem ID="toolbarAlerts" runat="server" Text="Alerts" />
</Items>
</telerik:RadMenu>
</div>
</form>
</body>
<script type="text/javascript">
$telerik.$(document).ready(function () {
$telerik.$("#toolbarAlerts").addClass("TopToolbarAlert");
});
</script>
</html>