Java Code:
import org.eclipse.swt.SWT;
import org.eclipse.swt.events.PaintEvent;
import org.eclipse.swt.events.PaintListener;
import org.eclipse.swt.layout.FillLayout;
import org.eclipse.swt.widgets.Canvas;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;

public class XOR {
  Display display = new Display();
  Shell shell = new Shell(display);

  public XOR() {
    shell.setLayout(new FillLayout());
    final Canvas canvas = new Canvas(shell, SWT.NULL);
    canvas.setBackground(display.getSystemColor(SWT.COLOR_WHITE));
    canvas.addPaintListener(new PaintListener() {
      public void paintControl(PaintEvent e) {
        e.gc.setXORMode(true);
        e.gc.setBackground(display.getSystemColor(SWT.COLOR_GREEN));
        e.gc.fillOval(60, 10, 100, 100); // Top 
        e.gc.setBackground(display.getSystemColor(SWT.COLOR_RED));
        e.gc.fillOval(10, 60, 120, 120); // left bottom    
        e.gc.setBackground(display.getSystemColor(SWT.COLOR_BLUE));
        e.gc.fillOval(110, 60, 100, 100); // right bottom    
      }
    });
    shell.setSize(300, 220);
    shell.open();
    //textUser.forceFocus();

    // Set up the event loop.
    while (!shell.isDisposed()) {
      if (!display.readAndDispatch()) {
        // If no more entries in event queue
        display.sleep();
      }
    }

    display.dispose();
  }

  private void init() {

  }

  public static void main(String[] args) {
    new XOR();
  }
}