Define Animation Trigger and StoredBoard for Ellipse
<Window x:Class="Main" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="" Height="600" Width="600"> <UniformGrid> <Ellipse Height="200" Width="200" Fill="Firebrick"> <Ellipse.Triggers> <EventTrigger RoutedEvent="Ellipse.Loaded"> <BeginStoryboard> <Storyboard AutoReverse="True" RepeatBehavior="Forever"> <ColorAnimation Storyboard.TargetProperty="Fill.Color" To="White" /> </Storyboard> </BeginStoryboard> </EventTrigger> </Ellipse.Triggers> </Ellipse> </UniformGrid> </Window>