<script type="text/javascript">
        //加載事件
        $(function () {
            var collection = $(".flag");
            $.each(collection, function () {
                $(this).addClass("start");
            });
        });
        //單擊事件
        function dj(dom) {
            var collection = $(".flag");
            $.each(collection, function () {
                $(this).removeClass("end");
                $(this).addClass("start");
            });
            $(dom).removeClass("start");
            $(dom).addClass("end");
        }
</script>

<style type="text/css">
        .start
        {
            cursor:pointer;
            color:Green;   
        }
        .end
        {
            cursor:pointer;
            color:Red;
        }
</style>

<span class="flag" onclick="dj(this)">LoveOne</span>
<span class="flag" onclick="dj(this)">LoveTwo</span>
<span class="flag" onclick="dj(this)">LoveThree</span>
<span class="flag" onclick="dj(this)">LoveFour</span>