how change background color when attempt the answer 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 ...

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.

}

}

design code: