You could do this using a
ColorAnimationUsingKeyFrames
as in the following sample:
<Window
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
x:Class="FadeSample.Window1"
x:Name="Window"
Title="Window1"
Width="640" Height="480">
<Window
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
x:Class="FadeSample.Window1"
x:Name="Window"
Title="Window1"
Width="640" Height="480">
<Window.Resources>
<Storyboard x:Key="OnClick1">
<ColorAnimationUsingKeyFrames
BeginTime="00:00:00" Storyboard.TargetName="button"
Storyboard.TargetProperty="(Panel.Background).(SolidColorBrush.Color)">
<SplineColorKeyFrame KeyTime="00:00:01" Value="#FFEF1407"/>
</ColorAnimationUsingKeyFrames>
</Storyboard>
</Window.Resources>
<Window.Triggers>
<EventTrigger
RoutedEvent="ButtonBase.Click" SourceName="button">
<BeginStoryboard Storyboard="{StaticResource OnClick1}"/>
</EventTrigger>
</Window.Triggers>
<Grid x:Name="LayoutRoot">
<Button
HorizontalAlignment="Left"
VerticalAlignment="Top"
Content="Button"
RenderTransformOrigin="3.339,5.055"
Margin="120,115,0,0"
Background="#FFDF891A"
x:Name="button"/>
</Grid>
</Window>