Heres what I use for what its worth.
in code objects edit like this.rgDailyResults.HeaderStyle =color.green or else you have tags in web and forms that control them like so:
<telerik:RadGrid ID="rgScenarioRollUps" AllowMultiRowSelection="True" AllowPaging="False" AllowSorting="False" Width="100px" AutoGenerateColumns="false" runat="server" Skin="">
<HeaderStyle CssClass="propGridHeader" />
<AlternatingItemStyle CssClass="propDarkGrid" />
<ItemStyle CssClass="propLightGrid" />
<SelectedItemStyle CssClass="propSelected" />
Edit This is what you wanted from telerik
http://www.telerik.com/help/winforms/
the latter link explains changing the "header image"