WPF - Animation on SelectionChanged

How would I go about changing a TabItem color from it's unselected color to it's selected color with an animation on SelectionChanged, so that both the unselected and selected TabItems change?

Edit: This is how my CustomTemplate looks like. There is no animation happening at all so what have I done wrong?

 <Style TargetType="TabItem">
        <Setter Property="IsEnabled" Value="False" />
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="TabItem">
                    <Grid>
                        <Border Bor开发者_运维百科derBrush="Transparent" BorderThickness="0" MinWidth="120">
                            <StackPanel Orientation="Vertical">
                                <ContentPresenter HorizontalAlignment="Center" ContentSource="Header" />
                                <Ellipse Name="Ellipse" Stroke="Black" StrokeThickness="1" Width="24" Height="24" Margin="5" Fill="Transparent" />
                            </StackPanel>
                        </Border>
                    </Grid>
                    <ControlTemplate.Triggers>
                        <MultiTrigger>
                            <MultiTrigger.Conditions>
                                <Condition Property="IsSelected" Value="True" />
                                <Condition Property="Ellipse.Fill" Value="Transparent" />
                            </MultiTrigger.Conditions>
                            <MultiTrigger.EnterActions>
                                <BeginStoryboard>
                                    <Storyboard>
                                        <ColorAnimation Storyboard.TargetName="Ellipse" Storyboard.TargetProperty="Fill"
                                                        From="Transparent" To="Orange" Duration="0:0:1" />
                                    </Storyboard>
                                </BeginStoryboard>
                            </MultiTrigger.EnterActions>
                        </MultiTrigger>
                        <MultiTrigger>
                            <MultiTrigger.Conditions>
                                <Condition Property="IsSelected" Value="False" />
                                <Condition Property="Ellipse.Fill" Value="Orange" />
                            </MultiTrigger.Conditions>
                            <MultiTrigger.EnterActions>
                                <BeginStoryboard>
                                    <Storyboard>
                                        <ColorAnimation Storyboard.TargetName="Ellipse" Storyboard.TargetProperty="Fill"
                                                        From="Orange" To="Transparent" Duration="0:0:1" />
                                    </Storyboard>
                                </BeginStoryboard>
                            </MultiTrigger.EnterActions>
                        </MultiTrigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

You can define custom TabItem template and run animations using triggers.