While adding an effect to viewbox the object is grayed out

I have added an effect to Viewbox as below:

<Viewbox Height="40" Width="40" HorizontalAlignment="Right" VerticalAlignment="Top" Margin="0,12.5,65,0" >
    <Viewbox.Effect>
        <effects:RippleEffect Magnitude="0" Frequency="0" />
    </Viewbox.Effect>
    <Grid>
        <Rectangle x:Name="MinimizeRect" RadiusX="7" RadiusY="7" StrokeThickness="2" Stroke="White" Fill="Transparent"/>
        <Image Source="Images/Minimize.png" Margin="5"/>
    </Grid>
    <Viewbox.Triggers>
        <EventTrigger RoutedEvent="Mouse.MouseEnter" >
            <BeginStoryboard>
                <Storyboard>
                    <DoubleAnimation Storyboard.TargetProperty="(Effect).Magnitude" To="0.1" Duration="0:0:0.3" AutoReverse="True" RepeatBehavior="Forever" />
                    <DoubleAnimation Storyboard.TargetProperty="(Effect).Frequency" To="40" Duration="0:0:0.3" AutoReverse="True" RepeatBehavior="Forever"/>
                    <ColorAnimation Storyboard.TargetProperty="(Rectangle.Fill).(SolidColorBrush.Color)" To="DodgerBlue" Duration="0:0:0.3" Storyboard.TargetName="MinimizeRect"/>
                </Storyboard>
            </BeginStoryboard>
        </EventTrigger>
        <EventTrigger RoutedEvent="Mouse.MouseLeave" >
            <BeginStoryboard>
                <Storyboard>
                    <DoubleAnimation Storyboard.TargetProperty="(Effect).Magnitude" To="0" Duration="0:0:0.3" />
                    <DoubleAnimation Storyboard.TargetProperty="(Effect).Frequency" To="0" Duration="0:0:0.3" />
                    <ColorAnimation Storyboard.TargetProperty="(Rectangle.Fill).(SolidColorBrush.Color)" To="Transparent" Duration="0:0:0.3" Storyboard.TargetName="MinimizeRect"/>
                </Storyboard>
            </BeginStoryboard>
        </EventTrigger>
    </Viewbox.Triggers>
</Viewbox>

But my image and Stroke of rectangle does not remain white. They are grayed. What might be the problem here?

Here is the image.

In the above image Ripple effect is added to Minimize button. Any effect is not added to close button.