テーブルの背景色を列ごとに変更する

JavaScript 
<script type="text/javascript">
    MyLib.event.observe(window, "load", function(){
        tableColumnColor("column-color", "even", "odd");
    }, false);
</script>
</head>
<body>
<table class="column-color" border="0" cellspacing="1" cellpadding="0">

td.odd {
    background-color: #fff;
}
td.even {
    background-color: #f0f0f6;
}

function tableColumnColor(classNameTable, classNameEven, classNameOdd){
    var table;
    var children;
    var tables = document.getElementsByTagName("table");

    classNameEven = classNameEven ? classNameEven : "even";
    classNameOdd = classNameOdd ? classNameOdd : "odd";

    for(var i=0; table=tables[i]; i++){
        if(table.className.indexOf(classNameTable, 0) != -1){
            var row;
            var rows = table.getElementsByTagName("tr");

            for(var j=0; row=rows[j]; j++){
                var column;
                var columns = row.getElementsByTagName("td");

                for(var k=0; column=columns[k]; k++){
                    if(k % 2 != 0){
                        column.className = classNameEven;
                    }else{
                        column.className = classNameOdd;
                    }
                }
            }
        }
    }
}