Setting DropDown ListItem Options in C# conditionally

Inside a gridview, I have the following footer template:
<FooterTemplate>
     <asp:DropDownList ID="New_Status" runat="server" Width="200px" >
          <asp:ListItem>Green</asp:ListItem>
          <asp:ListItem>Yellow</asp:ListItem>
          <asp:ListItem>Red</asp:ListItem>
     </asp:DropDownList>
</FooterTemplate>
Depending on certain variables that I have in the code behind, I want to change the dropdown to include on "Grey" and "Blue" as options. I'm new to asp, and would appreciate help on this.
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