Set different colors in ASP.Net Pie chart

Hi,

Am working in asp.net4.5 and facing problem piechart rendering.

Here is the code:

<div>
        <asp:Chart ID="WebChart1" runat="server">
            <%--<Series>
                <asp:Series Name="Series1" ChartType="Pie"></asp:Series>
            </Series>
            <ChartAreas>
                <asp:ChartArea Name="ChartArea1"></asp:ChartArea>
            </ChartAreas>--%>
            <Titles>
        <asp:Title ShadowOffset="3" Name="Items" />
    </Titles>
    <Legends>
        <asp:Legend Alignment="Center" Docking="Bottom" IsTextAutoFit="False" Name="Default" LegendStyle="Row" />
    </Legends>
        </asp:Chart>
    </div>

c#

protected void Page_Load(object sender, EventArgs e)
        {
            //double[] yValues = { 10, 27.5, 7, 12, 45.5 };
            //string[] xNames = { "Mike", "John", "William", "George", "Alex" };
            //WebWebChart1.Series[0].Points.DataBindXY(xNames, yValues);
            WebChart1.ChartAreas.Clear();
            WebChart1.Series.Clear();

            ChartArea area = new ChartArea("AREA");
            WebChart1.ChartAreas.Add(area);
            Series series = new Series("SERIES");
            WebChart1.Series.Add(series);
            series.IsValueShownAsLabel = true;
            series.ChartType = SeriesChartType.Pie;
            series.IsValueShownAsLabel = true;

            //Add data to the series.
            //See Alex Gorev's blog or the Samples Environment for different data binding methods.

            string[] xValues = {
	                            "Good Score",
	                            "Poor Score",
	                            "Average Score",
                                "Good Score",
                                "Average Score"                               
                                };
            double[] yValues = {
	                                100,
	                                24,
	                                47,
                                    77,
                                    55
                                };

            series.Points.DataBindXY(xValues,yValues);

            foreach (DataPoint dp in series.Points)
            {
                dp["Exploded"] = "True";
                dp["PieLabelStyle"] = "Inside";
                if (dp.YValues[0] <= 39)
                {
                    dp.LegendText = ">=39";
                    dp.Color = System.Drawing.Color.Red;
                }
                if (dp.YValues[0] > 39 && dp.YValues[0] < 70)
                {
                    dp.LegendText = "40 to 69";
                    dp.Color = System.Drawing.Color.Yellow;
                }
                if (dp.YValues[0] > 69)
                {
                    dp.LegendText = "> 70";
                    dp.Color = System.Drawing.Color.FromArgb(121, 167, 118);
                }
                //dp.Label = "#PERCENT";
                //dp["PieLineColor"] = "Red";
            }
            WebChart1.ChartAreas["AREA"].Area3DStyle.Enable3D = true;
            //WebChart1.ChartAreas["AREA"].Area3DStyle.Inclination = -25;
            WebChart1.Legends[0].Enabled = true;
            //WebChart1.Series[0].Label = "#VALX (#PERCENT{P0})";
            WebChart1.Series[0].Label = "#PERCENT{P0}";
        }

when i run this am able to see two yello color and two green color and one red color datapoint in my piechart. how to i club the datapoint to show one green color, one yello color and one redcolor datapoint. because i should have only three colors with three area of plotting. can anyone please help me to club the plotted  area of the same color as one