How to change the color of Radwindow loading image to blue

I hav开发者_开发技巧e radgrid on click of add new record, my radwindow opens up with loading image in green color but i want that to be changed to blue color, and my radwindow skin should remain black only.

This is my code where i am setting the property for radwindow

<telerik:RadWindowManager ID="RadWindowManager1" runat="server" EnableShadow="true"
                        Skin="Black" >
                        <Windows>
                            <telerik:RadWindow ID="UserListDialog" runat="server" Height="620px" Width="620px"
                                ReloadOnShow="true" ShowContentDuringLoad="false" Modal="true" VisibleStatusbar="false" Animation="Resize"  AutoSize="false" Behaviors="Close"/>
                        </Windows>
                    </telerik:RadWindowManager> 

You can examine the resulting markup with a tool like FireBug and copy the needed CSS selector. Here is an example yielded in the same manner:

        .RadWindow_Black td.rwWindowContent.rwLoading
    {
        background-image: url("custom-loading-image.gif") !important;
    }

Where, of course, the custom-loading-image.gif is your version of the loading sign that you wish to have and this CSS rule should be added to the head of the page in the tag. This information, along with some more useful tips is available in their Knowledge Base section: http://www.telerik.com/support/kb/aspnet-ajax/window/custom-loading-sign-for-radwindow.aspx.