Code

<d:Diagram x:Name="diagram"
	LinkCreated="diagram_LinkCreated"
	LinkModifying="diagram_LinkModifying"
	LinkModified="diagram_LinkModified">
</d:Diagram>



private SolidColorBrush brush;
private Color color;
private bool isStarted = false;
private Storyboard sb;

private void InitAnimation()
{
	brush = new SolidColorBrush(Colors.Green);

	sb = new Storyboard();
	ColorAnimation ca = new ColorAnimation();
	ca.From = Colors.Red;
	ca.To = Colors.Blue;
	ca.RepeatBehavior = RepeatBehavior.Forever;
	ca.Duration = new Duration(TimeSpan.FromMilliseconds(100));
	sb.Children.Add(ca);
	Storyboard.SetTarget(ca, brush);
	Storyboard.SetTargetProperty(ca, new PropertyPath("(SolidColorBrush.Color)"));
}

void diagram_LinkCreated(object sender, LinkEventArgs e)
{
	e.Link.Pen = new Pen(brush, 2, DashStyles.Solid);
}

void diagram_LinkModified(object sender, LinkEventArgs e)
{
	sb.Stop();
	isStarted = false;
}

void diagram_LinkModifying(object sender, LinkValidationEventArgs e)
{
	if (!isStarted)
	{
		isStarted = true;
		sb.Begin();
	}
}