Adding javascript validation to Textbox in GridView item template column

hello friend i have you can modified this code to applied you validation logic. i have added simple validation like if the textbox value is more then 4 character then it will displayed in red or it will green.

<asp:gridview id="grdView" runat="server" autogeneratecolumns="false" xmlns:asp="#unknown">
            <columns>
                <asp:templatefield headertext="Validation">
                    <itemtemplate>
                        <asp:textbox id="txtValidation" runat="server"></asp:textbox>
                    </itemtemplate>
                </asp:templatefield>
            </columns>
        </asp:gridview>

<script type="text/javascript">
        $(document).ready(function () {
            $('[id*="txtValidation"]').blur(function () {
                if ($(this).val().length > 4) {
                    $(this).css("color", "red");
                }
                else {
                    $(this).css("color", "green");
                }
            });
        });
    </script>