Код:
<script type="text/javascript">
    var td = document.getElementsByClassName("tcl")
    for(i=0;i<td.length;i++){
    td[i].setAttribute("onmouseover", "this.style.backgroundColor='red'")
    td[i].setAttribute("onmouseout", "this.style.backgroundColor=''")
    }
    </script>

red - меняем на свой цвет