<table> 
 <tr> 
 <td> 
 <asp:DropDownList ID ="ddlMultiColor" 
 OnSelectedIndexChanged="ddlMultiColor_OnSelectedIndexChanged" 
 runat="server" AutoPostBack="true"> 
 </asp:DropDownList> 
 </td> 
 <td> 
 <div id="msgColor" runat="server"> 
 </div> 
 </td> 
 </tr> 
 </table>

 using System; 
 using System.Web; 
 using System.Reflection; 
 using System.Drawing; 
 using System.Collections.Generic;

 protected void Page_Load(object sender, EventArgs e) 
 { 
 if (Page.IsPostBack == false) 
 { 
 populateDdlMultiColor(); //51aspx.com 
 colorManipulation(); 
 } 
 }

 private void populateDdlMultiColor() 
 { 
 ddlMultiColor.DataSource = finalColorList(); 
 ddlMultiColor.DataBind(); // 
 }

 finalColorList()方法

 private List finalColorList() 
 { 
 string[] allColors = Enum.GetNames(typeof(System.Drawing.KnownColor)); 
 string[] systemEnvironmentColors = 
 new string[( 
 typeof(System.Drawing.SystemColors)).GetProperties().Length]; 
 
 int index = 0; 
 
 foreach (MemberInfo member in ( 
 typeof(System.Drawing.SystemColors)).GetProperties()) 
 { 
 systemEnvironmentColors[index ++] = member.Name; 
 } 
 List finalColorList = new List(); 
 foreach (string color in allColors) 
 { 
 if (Array.IndexOf(systemEnvironmentColors, color) < 0) 
 { 
 finalColorList.Add(color); 
 } 
 } 
 return finalColorList; 
 }

 private void colorManipulation() 
 { 
 int row; 
 for (row = 0; row < ddlMultiColor.Items.Count - 1; row++) 
 { 
 ddlMultiColor.Items[row].Attributes.Add("style", 
 "background-color:" + ddlMultiColor.Items[row].Value); 
 } 
 ddlMultiColor.BackColor = 
 Color.FromName(ddlMultiColor.SelectedItem.Text);//liudao翻译 
 }

 protected void ddlMultiColor_OnSelectedIndexChanged(object sender, 
 EventArgs e) 
 { 
 ddlMultiColor.BackColor = Color.FromName(ddlMultiColor.SelectedItem.Text); 
 colorManipulation(); 
 ddlMultiColor.Items.FindByValue(ddlMultiColor.SelectedValue).Selected = 
 true; 
 msgColor.Attributes.Add("style", "background:" + 
 ddlMultiColor.SelectedItem.Value + ";width:30px;height:25px;"); 
 }