C# 如何在OpenXMLC.net中手动定义颜色代码？

我可以创建一个谷歌饼图，但导出到MS Word的地方只有默认的MS Word颜色。那么，如何以开放xml样式手动定义颜色代码呢？下面我添加了当触发导出按钮单击事件时的c代码

  protected void btnExport_Click(object sender, EventArgs e)
{  

    CreateWordChart createWordChart = null;
    try
    {
        Random r = new Random();
        string p = @"E:/File/Graph" + r.Next(1, 20000) + ".docx";
        FileStream fs = File.Create(p);
        fs.Close();       

        createWordChart = new CreateWordChart(p);
        List<ChartSubArea> chartAreas = new List<ChartSubArea>();
        SqlConnection conn = new SqlConnection("Data Source=10.0.0.101; uid=sa; pwd=sql;database=QuestionDB;");
        DataSet ds = new DataSet();
        DataTable dt = new DataTable();
        conn.Open();
        string cmdstr = "select top 5 First_name, COUNT(Department) [Department] from Employee group by First_name";
        SqlCommand cmd = new SqlCommand(cmdstr, conn);
        SqlDataAdapter adp = new SqlDataAdapter(cmd);
        adp.Fill(ds);           
        ds.Tables[0].Columns.Add("Column1", typeof(string));


        System.Drawing.Color[] colorSet = new System.Drawing.Color[4] { System.Drawing.Color.Red, System.Drawing.Color.Blue, System.Drawing.Color.Green, System.Drawing.Color.Purple };


        dt = ds.Tables[0];

        string cat = "";
        string val = "";
        int i = 0;
        foreach (DataRow dr in dt.Rows)
        {
            cat = dr[0].ToString();
            val = dr[1].ToString();

            chartAreas.Add(new ChartSubArea() { ColorDra = *colorSet*, Label = cat, Value = val });            
            i = i + 1;
        }
        createWordChart.CreateChart(chartAreas);
    }
    catch (Exception ex)
    {
        throw ex;
    }
    finally
    {
        if (createWordChart != null)
        {
            createWordChart.Dispose();
        }
    }
}

 public class ChartSubArea
{
    public System.Drawing.Color[] ColorDra { get; set; }
    public Shading purecolor { get; set; }
    public SchemeColorValues Color { get; set; }
    public String Label { get; set; }
    public string Value { get; set; }
}

提前谢谢