MainPage.xaml.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices.WindowsRuntime;
using Windows.Foundation;
using Windows.Foundation.Collections;
using Windows.UI;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Controls.Primitives;
using Windows.UI.Xaml.Data;
using Windows.UI.Xaml.Input;
using Windows.UI.Xaml.Media;
using Windows.UI.Xaml.Navigation;

// The Blank Page item template is documented at https://go.microsoft.com/fwlink/?LinkId=402352&clcid=0x409

namespace Wooosh
{
    /// <summary>
    /// An empty page that can be used on its own or navigated to within a Frame.
    /// </summary>
    public sealed partial class MainPage : Page
    {
        public MainPage()
        {
            this.InitializeComponent();
        }

        private void circle1_PointerEntered(object sender, PointerRoutedEventArgs e)
        {

            // Create a SolidColorBrush with a red color to fill the 
            // Ellipse with.
            SolidColorBrush mySolidColorBrush = new SolidColorBrush();

            // Describes the brush's color using RGB values. 
            // Each value has a range of 0-255.
            mySolidColorBrush.Color = Color.FromArgb(255, 255, 255, 0);
            circle1.Fill = mySolidColorBrush;

        }

        private void Bob_PointerExited(object sender, PointerRoutedEventArgs e)
        {
            // Create a SolidColorBrush with a red color to fill the 
            // Ellipse with.
            SolidColorBrush mySolidColorBrush = new SolidColorBrush();

            // Describes the brush's color using RGB values. 
            // Each value has a range of 0-255.
            mySolidColorBrush.Color = Color.FromArgb(0, 0, 255, 0);
            circle1.Fill = mySolidColorBrush;
        }
    }
}