Change TextBox placeholder color on Button click using JavaScript and jQuery in ASP.Net

<style type="text/css">
    .Red::-webkit-input-placeholder
    {
        color: red; /* WebKit, Blink, Edge */
    }
    .Red:-moz-placeholder
    {
        color: red; /* Mozilla Firefox 4 to 18 */
    }
    .Red::-moz-placeholder
    {
        color: red; /* Mozilla Firefox 19+ */
    }
    .Red::-ms-input-placeholder
    {
        color: red; /* Microsoft Edge */
    }
    .Red:-ms-input-placeholder
    {
        color: red; /* Internet Explorer 10-11 */
    }
    .Red::placeholder
    {
        color: red; /* Most modern browsers support this now. */
    }
</style>
<script type="text/javascript">
    function ChangePlaceHolderColor() {
        var textBoxes = document.getElementsByTagName("input");
        for (var i = 0; i < textBoxes.length; i++) {
            if (textBoxes[i].type == "text") {
                if (!textBoxes[i].value) {
                    textBoxes[i].className += " Red";
                }
            }
        }
    }
</script>
<div>
    <input name="txtfirstName" type="text" id="txtfirstName" placeholder="First Name" />
    <input name="txtlastName" type="text" id="txtlastName" placeholder="Last Name" />
    <input type="button" name="Button1" value="Register" onclick="ChangePlaceHolderColor();" />
</div>

<style type="text/css">
    .Red::-webkit-input-placeholder
    {
        color: red; /* WebKit, Blink, Edge */
    }
    .Red:-moz-placeholder
    {
        color: red; /* Mozilla Firefox 4 to 18 */
    }
    .Red::-moz-placeholder
    {
        color: red; /* Mozilla Firefox 19+ */
    }
    .Red::-ms-input-placeholder
    {
        color: red; /* Microsoft Edge */
    }
    .Red:-ms-input-placeholder
    {
        color: red; /* IE 10-11 */
    }
    .Red::placeholder
    {
        color: red; /* Modern browsers */
    }
</style>
<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
<script type="text/javascript">
    $(function () {
        $('[id*=Button1]').on("click", function () {
            $('input[type=text]').each(function () {
                if (!$(this).val()) {
                    $(this)[0].className += " Red";
                }
            });
        });
    });
</script>
<div>
    <input name="txtfirstName" type="text" id="txtfirstName" placeholder="First Name" />
    <input name="txtlastName" type="text" id="txtlastName" placeholder="Last Name" />
    <input type="button" id="Button1" value="Register" />
</div>