New Post: Customise AvalonDock style

I would like to be able to customise the style, e.g. colours, of the AvalonDock controls.

However I don't want to just edit the supplied style file, e.g. generic.xaml. My application allows the user to change the theme at runtime, so I supply two ResourceDictionary files which have different colour definitions for a number of controls.
It is in these ResourceDictionary files that I would like to override the default AvalonDock colours but I can't seem to get it to work.

I can see a change in colour if I add say

<Setter Property="Background" Value="Red"/>

in generic.xaml i.e.
<!--DocumentPaneControlStyle-->

<Style x:Key="DocumentPaneControlStyle" TargetType="{x:Type avalonDockControls:LayoutDocumentPaneControl}">
    <Setter Property="Background" Value="Red"/>
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type avalonDockControls:LayoutDocumentPaneControl}">

....

but if I do something similar in my ResourceDictionary nothing happens.

Any help much appreciated.