ASP.NET TreeView control

I am using asp.net treeview in my website and I am using LevelStyles element to change forecolor for each level.
the problem is that forecolor is not applied and all tree nodes are still blue color,default color, but other attributes is working fine such as Font-Bold.
here is my code
<asp:TreeView ID="tv" runat="server" > <Nodes> <asp:TreeNode Text="Figure 1.1"> <asp:TreeNode Text="Figure 1.1.1"></asp:TreeNode> </asp:TreeNode> </Nodes> <LevelStyles> <asp:TreeNodeStyle Font-Bold="true" ForeColor="Yellow" /> <asp:TreeNodeStyle Font-Bold="false" ForeColor="Red" /> </LevelStyles> </asp:TreeView> Any help?