You should be able to get it done with some quick jQuery
http://docs.jquery.com/CSS/css#namevalue
$telerik.$("#'<%=myTextBox.ClientID %>'")
.mouseover(function () {
$telerik.
$(this).css("color","red");
});
Here's the events you can use
http://docs.jquery.com/Events
jQuery comes embedded into most of the telerik components, just make sure to use $telerik.$ instead of just $.
Give it a try, you can do some awesome stuff with jQuery, and like I said, it comes built into the Telerik.Web.UI anyway!
Steve