<Window
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    x:Class="WpfApplication1.MainWindow"
    x:Name="Window"
    Title="MainWindow"
    Width="640" Height="480">
    <Window.Resources>
        <Storyboard x:Key="Storyboard1">
            <ColorAnimationUsingKeyFrames Storyboard.TargetProperty="(Shape.Fill).(SolidColorBrush.Color)" Storyboard.TargetName="rectangle">
                <EasingColorKeyFrame KeyTime="0" Value="#FF131360"/>
                <EasingColorKeyFrame KeyTime="0:0:2" Value="#FF13601F"/>
            </ColorAnimationUsingKeyFrames>
        </Storyboard>
    </Window.Resources>
    <Window.Triggers>
        <EventTrigger RoutedEvent="FrameworkElement.Loaded">
            <BeginStoryboard Storyboard="{StaticResource Storyboard1}"/>
        </EventTrigger>
    </Window.Triggers>

    <Grid x:Name="LayoutRoot">
        <Rectangle x:Name="rectangle" Fill="#FFF4F4F5" Height="60" Margin="205,144,296,0" Stroke="Black" VerticalAlignment="Top"/>
    </Grid>
</Window>