<Grid x:Name="LogoGrid">
    <Grid.Resources>
        <Storyboard x:Name="LoadingStoryBoard">
            <ColorAnimationUsingKeyFrames
                Storyboard.TargetName="LogoGrid"
                Storyboard.TargetProperty="(UIElement.Background).(LinearGradientBrush.GradientStops)[1].(GradientStop.Color)"
                RepeatBehavior="Forever"
                EnableDependentAnimation="True">
                <LinearColorKeyFrame Value="#FFFF0000" KeyTime="0:0:1" />
                <LinearColorKeyFrame Value="#FFFFFF00" KeyTime="0:0:2" />
            </ColorAnimationUsingKeyFrames>
        </Storyboard>
    </Grid.Resources>
    <Grid.Background>
        <LinearGradientBrush StartPoint="0,0" EndPoint="1,1">
            <GradientStop Color="Transparent" Offset="0" />
            <GradientStop Color="#FFFFFF00" Offset="0.5" /><!-- Animation target -->
            <GradientStop Color="Transparent" Offset="1" />
        </LinearGradientBrush>
    </Grid.Background>
</Grid>

public sealed partial class MainPage
{
    public MainPage()
    {
        InitializeComponent();
        Loaded += (sender, args) => LoadingStoryBoard.Begin();
    }
}