<Button Name="btn1" Background="Pink" 
        BorderBrush="Black" BorderThickness="1" 
        Click="OnClick1" ClickMode="Hover">
  ClickMe1
</Button>

<Button Name="btn2" Background="LightBlue" 
        BorderBrush="Black" BorderThickness="1" 
        Click="OnClick2" ClickMode="Press">
  ClickMe2
</Button>

<Button Name="btn3" 
        Click="OnClick3" ClickMode="Release">
  Reset
</Button>

Private Sub OnClick1(ByVal sender As Object, ByVal e As RoutedEventArgs)
    btn1.Background = Brushes.LightBlue
End Sub

Private Sub OnClick2(ByVal sender As Object, ByVal e As RoutedEventArgs)
    btn2.Background = Brushes.Pink
End Sub

Private Sub OnClick3(ByVal sender As Object, ByVal e As RoutedEventArgs)
    btn1.Background = Brushes.Pink
    btn2.Background = Brushes.LightBlue
End Sub

        void OnClick1(object sender, RoutedEventArgs e)
        {
            btn1.Background = Brushes.LightBlue;
        }

        void OnClick2(object sender, RoutedEventArgs e)
        {
            btn2.Background = Brushes.Pink;
        }

        void OnClick3(object sender, RoutedEventArgs e)
        {
            btn1.Background = Brushes.Pink;
            btn2.Background = Brushes.LightBlue;
        }