Hello Ed,

Thank you for your post. I have been looking into it and I can suggest you the following Styles for HeaderCellControl and ExpansionIndicatorHeaderCellControl in order to achieve the result you want:

<Style TargetType="{x:Type igPrim:ExpansionIndicatorHeaderCellControl}">
    <Setter Property="Background" Value="YellowGreen"/>
</Style>
<Style TargetType="{x:Type igPrim:HeaderCellControl}">
    <Style.Triggers>
        <DataTrigger Binding="{Binding RelativeSource={RelativeSource Self},Path=Cell.Row.Level}" Value="1">
            <Setter Property="Background" Value="PeachPuff"/>
        </DataTrigger>
    </Style.Triggers>
    <Setter Property="Background" Value="YellowGreen"/>
</Style>

Basically I used DataTrigger to apply different Background to the first and second ColumnLayout. Please let me know if this helps you or you need further assistance on this matter.

Looking forward for your reply.