让TextBlock文字变化的动画

<TextBlock>
            <TextBlock.Triggers>
                <EventTrigger RoutedEvent="Loaded">
                    <BeginStoryboard>
                        <Storyboard>
                            <ColorAnimation Storyboard.TargetName="color"
                                            Storyboard.TargetProperty="Color"
                                            From="Red" To="Green" Duration="0:0:0.5"
                                            RepeatBehavior="Forever" AutoReverse="True"/>
                        </Storyboard>
                    </BeginStoryboard>
                </EventTrigger>
            </TextBlock.Triggers>
            one 
            <Run>
                <Run.Foreground>
                    <SolidColorBrush x:Name="color" Color="Red"/>                                                         
                </Run.Foreground>    
                two 
            </Run>            
            three
        </TextBlock>