Changing Background color and borders ASP.Net DataGrid's ToolTip

I'm using ASP.Net (VB.Net) 2005. Working specifically with the Telerik RadGrid which is inherited from Microsoft's Datagrid.  I am reading my ToolTips from xml which I convert into a dataset and bind to the grid.  That part works fine.  My question is: What is an easy way to add a style to the ToolTip on the datagrid?  For example my tooltip's background needs to be blue with black borders. Here is a sniplet of how I am binding the data to the templategridcolumn and tooltip:
'******************Client side Code ******************************************
 <radG:GridTemplateColumn DataField="DESC"  Groupable="False" UniqueName="DESC" >
                            <ItemStyle horizontalalign="Left" VerticalAlign="Middle" Height="20px"></ItemStyle>
                            <headertemplate>T</headertemplate>
                            <itemtemplate>                                
                            <asp:Label id="lblDes" Runat="server"   ToolTip='<% #GetToolTip(Container.DataItem ,"DESC")%>'>
                            <%#FormatColumn(Container.DataItem, "DESC")%></asp:Label>
                            </itemtemplate>
                        </radG:GridTemplateColumn>

'*******************Code Behind**************
 Public Function GetToolTip(ByVal dRowView As DataRowView, ByVal colName As String, Optional ByVal desc As String = "") As String
        If (dRowView.Row.Table.Columns.Contains(colName)) Then
            If (Not IsDBNull(dRowView.Row.Item(colName))) Then
                If (colName = "DESC") Then
                    If (CType(dRowView.Row.Item(colName), String) = "FW") Then
                        Return "Forward Align"
                    ElseIf (CType(dRowView.Row.Item(colName), String) = "RE" Or CType(dRowView.Row.Item(colName), String) = "RW") Then
                        Return "Rear Wheel"
                    ElseIf (CType(dRowView.Row.Item(colName), String) = "BW") Then
                        Return "Back Wheel"
                    End If
                Else
                    Return desc
                End If
            Else
                Return String.Empty
            End If
        Else
            Return String.Empty
        End If
    End Function