in source code
design viiew
<asp:dropdownlist id="vv" runat="server" autopostback="True" forecolor="#FF3399" xmlns:asp="#unknown">
<asp:listitem value="0" text="1" style="color:Red;">
<asp:listitem value="1" text="2" style="color:Green;">
<asp:listitem value="2" text="3" style="color:Maroon;">
<asp:listitem value="3" text="4" style="color:Blue;">
<asp:textbox id="tt" runat="server" xmlns:asp="#unknown">
and server side put this code
in vb.net implement to c#
Protected Sub vv_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles vv.SelectedIndexChanged
tt.Text = vv.SelectedItem.ToString()
Dim al As ListItem = vv.SelectedItem
Dim s As String = al.Attributes("style").ToString.Substring(6)
s = s.Substring(0, s.Length - 1)
tt.ForeColor = Drawing.ColorTranslator.FromHtml(s)
End Sub