As a very simple example:
<Window.Resources>
<Style TargetType="Window" x:Key="windowStyleOne">
<Setter Value="123" Property="Content" />
<Setter Value="Red" Property="Background"/>
</Style>
<Style TargetType="Window" x:Key="windowStyleTwo">
<Setter Value="456" Property="Content" />
<Setter Value="Green" Property="Background" />
</Style>
</Window.Resources>
<Button Name ="myButtonOne" Click="ButtonOne_Click">Red</Button>
<Button Name="myButtonTwo" Click="ButtonTwo_Click">Green</Button>
private void ButtonOne_Click(object sender, RoutedEventArgs e)
{
this.Style = (Style)(this.Resources["windowStyleOne"]);
}
private void ButtonTwo_Click(object sender, RoutedEventArgs e)
{
this.Style = (Style)(this.Resources["windowStyleTwo"]);
}
EDIT: Actually heres an example that fits with your suggested example perfectly. myButtonOne makes the main window have a red background and myButtonTwo sets the window to have a green background.