how change background color when attempt the answer using radio button in asp.net
hi, i have one challenge, that is i am developing a one online examination website , in that when i am attempt the question ..., have to change the lable 1 back color is green , and when i am click on mark as review button it will shows the orange color ..how can i write code for that please help me...or send a reference  url to me..i am waitng for your reply...thank you .
my code is ...
 
<pre lang="C#">public partial class user_poexam : System.Web.UI.Page
{
  
    protected string PostBackStr;
    public static SqlConnection sqlconn;
    protected void Page_Load(object sender, EventArgs e)
    {
        sqlconn = new SqlConnection(ConfigurationManager.AppSettings["sqlconnstr"].ToString());
        // PostBackStr = Page.ClientScript.GetPostBackEventReference(this, "time");     
        if (!SM1.IsInAsyncPostBack)
        {
            Session["timeout"] = DateTime.Now.AddMinutes(30).ToString();
        }
        //if (IsPostBack)
        //{
           
        //    //string eventArg = Request["__EVENTARGUMENT"];
        //    //if (eventArg == "time")
        //    //{
        //    //    Response.Write("Timed out..please try again");
        //    //    //getNextQuestion();
        //    //}
        //}
        }
    protected void btn_next_Click(object sender, EventArgs e)
    {
        getNextQuestion();
    }
    protected void btn_startexam_Click(object sender, EventArgs e)
    {
        // Label1.Visible = false;
        //txtName.Visible = false;
        btn_startexam.Visible = false;
        Panel1.Visible = true;
        // lblName.Text = "Name : " + txtName.Text;
        int score = Convert.ToInt32(txtScore.Text);
        lblScore.Text = "Score : " + Convert.ToString(score);
        Session["counter"] = "1";
        Random rnd = new Random();
        int i = rnd.Next(1, 10);//Here specify your starting slno of question table and ending no.
        //lblQuestion.Text = i.ToString();
        getQuestion(i);
    }
    public void getQuestion(int no)
    {
        string str = "select * from Question where slNo=" + no + "";
        SqlDataAdapter da2 = new SqlDataAdapter(str, sqlconn);
        DataSet ds2 = new DataSet();
        da2.Fill(ds2, "Question");
        if (ds2.Tables[0].Rows.Count > 0)
        {
            DataRow dtr;
            int i = 0;
            while (i < ds2.Tables[0].Rows.Count)
            {
                dtr = ds2.Tables[0].Rows[i];
                Session["Answer"] = Convert.ToString(Convert.ToInt32(dtr["Correct"].ToString()) - 1);
                lblQuestion.Text = "Q." + Session["counter"].ToString() + "  " + dtr["Question"].ToString();
                RblOption.ClearSelection();
                RblOption.Items.Clear();
                RblOption.Items.Add(dtr["Option1"].ToString());
                RblOption.Items.Add(dtr["Option2"].ToString());
                RblOption.Items.Add(dtr["Option3"].ToString());
                RblOption.Items.Add(dtr["Option4"].ToString());
                i++;
            }
        }
    }
    //public void GetPrevQuestion(int prev)
    //{
    //    // dtr = (DataTable)ViewState["Datatable"];
    //    // dr = dtr.Rows[prev];
    //    // //Session["RblOption"] = (string)RblOption.SelectedValue;
    //    // //RblOption.SelectedValue = (string)Session["RblOption"];
    //    // lblQuestion.Text = "Q." + Session["counter"] + "  " + dr["Qn"].ToString();
    //    //// RblOption.ClearSelection();
    //    // RblOption.Items.Clear();
    //    // RblOption.Items.Add(dr["option1"].ToString());
    //    // RblOption.Items.Add(dr["option2"].ToString());
    //    // RblOption.Items.Add(dr["option3"].ToString());
    //    // RblOption.Items.Add(dr["option4"].ToString());
    //    if (prev != 0)
    //    {
    //        BtnPrev.Visible = true;
    //    }
    //    BtnNext.Visible = true;
    //}
    public void getNextQuestion()
    {
        if (Convert.ToInt32(Session["counter"].ToString()) < 10)//10 is a counter which is used for 10 questions
        {
            if (RblOption.SelectedIndex >= 0)
            {
                if (Session["Answer"].ToString() == RblOption.SelectedIndex.ToString())
                {
                    int score = Convert.ToInt32(txtScore.Text) + 1;// 1 for mark for each question
                    txtScore.Text = score.ToString();
                    lblScore.Text = "Score : " + Convert.ToString(score);
                }
            }
            Random rnd = new Random();
            int i = rnd.Next(1, 10);
            //lblQuestion.Text = i.ToString();
            getQuestion(i);
            Session["counter"] = Convert.ToString(Convert.ToInt32(Session["counter"].ToString()) + 1);
        }
        else
        {
            Panel2.Visible = false;
            //code for displaying after completting the exam, if you want to show the result then you can code here.
        }
    }</pre>
design code:
 <asp:UpdatePanel ID="UpdatePanel1" runat="server" UpdateMode="Conditional" >
        <ContentTemplate>
            <asp:Label ID="lbl_Timer" runat="server" Text="Label"></asp:Label>
            <asp:Button ID="btn_startexam" runat="server" CssClass="btn_examstart"  Text="Start Exam" ToolTip="Enter Your Name" OnClick="btn_startexam_Click"/>
               <asp:TextBox ID="txtScore" runat="server" Style="z-index: 103; left: 251px; position: relative;
            top: 276px" Visible="False" Width="63px">0</asp:TextBox>
            <asp:Panel ID="Panel1" runat="server" CssClass="pnl_exam1" Visible="false" >
                
                  <asp:Label ID="lblScore" runat="server" CssClass="lbl_score" Text="Score : " ></asp:Label>
                <asp:Panel ID="Panel3" runat="server" Height="14px" Width="119px" style="left:427px; z-index: 106; position: relative; top: 2px;">
            <span id="cd" style ="left:100px;"></span>
            </asp:Panel>
                  <asp:Panel ID="Panel2" runat="server" CssClass="pnl2_exam" >
                <asp:Label ID="lblQuestion" runat="server"  CssClass="lblquestion"></asp:Label>
                <asp:RadioButtonList ID="RblOption" runat="server" CssClass="rbtnanswer" >
                </asp:RadioButtonList>
            <asp:Button ID="btn_next" runat="server" CssClass="btn_examnext"  Text="Next" ToolTip="Click Here to Save and Take Next Question" OnClick="btn_next_Click" />
                <asp:Button ID="btn_mreview" runat="server" CssClass="btn_examreview"  Text="Mark as Review" ToolTip="Click Here to Mark as review"  />
                  <asp:Button ID="btn_mans" runat="server" CssClass="btn_exammanswer"  Text="Mark as Answer" ToolTip="Click Here to Mark as Answer"  />
              
            </asp:Panel>
               
                <asp:Panel ID="Panel4" runat="server" CssClass="pnl_side">
                    <div id="div_qviewback" style="padding-left:5px; padding-right:5px;">
                        <asp:Label ID="Label1" runat="server" Text="1"  CssClass="lbl_qviews" ></asp:Label>
                         <asp:Label ID="Label2" runat="server" Text="2"  CssClass="lbl_qviews" ></asp:Label>
                         <asp:Label ID="Label3" runat="server" Text="3"  CssClass="lbl_qviews" ></asp:Label>
                         <asp:Label ID="Label4" runat="server" Text="4"  CssClass="lbl_qviews" ></asp:Label>
                         <asp:Label ID="Label5" runat="server" Text="5"  CssClass="lbl_qviews" ></asp:Label>
                         <asp:Label ID="Label6" runat="server" Text="6"  CssClass="lbl_qviews" ></asp:Label>
                         <asp:Label ID="Label7" runat="server" Text="7"  CssClass="lbl_qviews" ></asp:Label>
                        <asp:Label ID="Label8" runat="server" Text="8"  CssClass="lbl_qviews" ></asp:Label>
                        <asp:Label ID="Label9" runat="server" Text="9"  CssClass="lbl_qviews" ></asp:Label>
                        <asp:Label ID="Label10" runat="server" Text="10"  CssClass="lbl_qviews" ></asp:Label>
                    </div>
                </asp:Panel>
                  </asp:Panel>
          
        </ContentTemplate>
                 <Triggers>
                     <asp:AsyncPostBackTrigger ControlID="timer1"  EventName="tick"/>
                 </Triggers>
    </asp:UpdatePanel>