How to Style the Selected PivotItem Header - windows-phone-8

Question

I am trying to implement a solution whereby the currently selected PivotItem Header Background is the PhoneAccentBrush, but all of the other pivot headers are a default color such as PhoneDisabledBrush. This way when the user swipes left or right, a PivotItem will come into view and its background color will change to the active PhoneAccentBrush, and all other pivot headers will remain with the default background color. How might I be able to do this?
Currently I have implemented what I want, except for the selected/nonselected pivot item backgrounds
<phone:PhoneApplicationPage.Resources>
<Style x:Key="PivotStyle1" TargetType="phone:Pivot">
<Setter Property="Margin" Value="0"/>
<Setter Property="Padding" Value="0"/>
<!--<Setter Property="Foreground" Value="{StaticResource PhoneForegroundBrush}"/>-->
<Setter Property="Foreground" Value="white"/>
<Setter Property="Background" Value="Transparent"/>
<Setter Property="ItemsPanel">
<Setter.Value>
<ItemsPanelTemplate>
<Grid/>
</ItemsPanelTemplate>
</Setter.Value>
</Setter>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="phone:Pivot">
<Grid HorizontalAlignment="{TemplateBinding HorizontalAlignment}" VerticalAlignment="{TemplateBinding VerticalAlignment}">
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<Grid Background="{StaticResource PhoneAccentBrush}" CacheMode="BitmapCache" Grid.RowSpan="2" />
<Grid Background="{TemplateBinding Background}" CacheMode="BitmapCache" Grid.Row="2" />
<ContentPresenter ContentTemplate="{TemplateBinding TitleTemplate}" Content="{TemplateBinding Title}" Margin="24,17,0,-7"/>
<Primitives:PivotHeadersControl x:Name="HeadersListElement" Grid.Row="1"/>
<ItemsPresenter x:Name="PivotItemPresenter" Margin="{TemplateBinding Padding}" Grid.Row="2"/>
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</phone:PhoneApplicationPage.Resources>
...
<!--Pivot Control-->
<phone:Pivot x:Name="Pivot" Style="{StaticResource PivotStyle1}">
...
</phone:Pivot>
Which looks like..
*Update
StackTrace Exception in the following update.. InvalidOperationException: Cannot resolve TargetProperty (Border.Background).(SolidColorBrush.Color) on specified object.
<Style x:Key="PivotHeaderItemStyle1" TargetType="Primitives:PivotHeaderItem">
<Setter Property="Background" Value="Transparent"/>
<Setter Property="Padding" Value="21,0,1,0"/>
<Setter Property="Margin" Value="0"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="Primitives:PivotHeaderItem">
<Grid>
<VisualStateManager.VisualStateGroups>
<VisualStateGroup x:Name="SelectionStates">
<VisualState x:Name="Unselected">
<Storyboard>
<ColorAnimation Duration="0" Storyboard.TargetName="myback" Storyboard.TargetProperty="(Border.Background).(SolidColorBrush.Color)" To="DarkGrey"/>
</Storyboard>
</VisualState>
<VisualState x:Name="Selected">
<Storyboard>
<ColorAnimation Duration="0" Storyboard.TargetName="myback" Storyboard.TargetProperty="(Border.Background).(SolidColorBrush.Color)" To="Red"/>
</Storyboard>
</VisualState>
</VisualStateGroup>
</VisualStateManager.VisualStateGroups>
<Border x:Name="myback">
<ContentControl x:Name="contentPresenter" ContentTemplate="{TemplateBinding ContentTemplate}" Content="{TemplateBinding Content}" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="{TemplateBinding Padding}" Opacity="{StaticResource PhonePivotUnselectedItemOpacity}"/>
</Border>
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<Style x:Key="PivotStyle1" TargetType="phone:Pivot">
<Setter Property="Margin" Value="0"/>
<Setter Property="Padding" Value="0"/>
<Setter Property="Foreground" Value="{StaticResource PhoneForegroundBrush}"/>
<Setter Property="Background" Value="Transparent"/>
<Setter Property="ItemsPanel">
<Setter.Value>
<ItemsPanelTemplate>
<Grid/>
</ItemsPanelTemplate>
</Setter.Value>
</Setter>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="phone:Pivot">
<Grid HorizontalAlignment="{TemplateBinding HorizontalAlignment}" VerticalAlignment="{TemplateBinding VerticalAlignment}">
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<Grid Background="{TemplateBinding Background}" Grid.RowSpan="3"/>
<ContentControl x:Name="TitleElement" ContentTemplate="{TemplateBinding TitleTemplate}" Content="{TemplateBinding Title}" HorizontalAlignment="Left" Margin="24,17,0,-7" Style="{StaticResource PivotTitleStyle}"/>
<Primitives:PivotHeadersControl x:Name="HeadersListElement" Grid.Row="1" ItemContainerStyle="{StaticResource PivotHeaderItemStyle1}"/>
<ItemsPresenter x:Name="PivotItemPresenter" Margin="{TemplateBinding Padding}" Grid.Row="2"/>
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>

Answer 1

K, seems you're getting there. The actions need to avoid code behind....
We're just going to add another storyboard animation for the background. And the simplest way I know how to do this is just add a border.
Add a Border around your < ContentControl x:Name="contentPresenter" /> so it looks like this
<Border x:Name="myback" Background="{TemplateBinding Background}">
<ContentControl x:Name="contentPresenter"/>
</Border>
Now lets color it based on the Selected State. Add in your other Storyboard animations as well.
<VisualStateManager.VisualStateGroups>
<VisualStateGroup x:Name="SelectionStates">
<VisualState x:Name="Unselected">
<Storyboard>
<ColorAnimation Duration="0" Storyboard.TargetName="myback" Storyboard.TargetProperty="(Border.Background).(SolidColorBrush.Color)" To="DarkGrey"/>
</Storyboard>
</VisualState>
<VisualState x:Name="Selected">
<Storyboard>
<ColorAnimation Duration="0" Storyboard.TargetName="myback" Storyboard.TargetProperty="(Border.Background).(SolidColorBrush.Color)" To="Red"/>
</Storyboard>
</VisualState>
</VisualStateGroup>
</VisualStateManager.VisualStateGroups>
Let me know it goes well :D