import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class ColorDnD extends JPanel {

    public ColorDnD() {
        setLayout(new GridLayout(0, 1));

	JPanel from = new JPanel();
	from.setBackground(Color.blue);
	add(from);
        from.setTransferHandler(new TransferHandler("background"));
	from.addMouseListener(new MouseAdapter() {
		public void mousePressed(MouseEvent e) {
		    JComponent c = (JComponent)e.getSource();
		    TransferHandler th = c.getTransferHandler();
		    th.exportAsDrag(c, e, TransferHandler.COPY);
		}
	    });
	
	
	JPanel to = new JPanel();
	to.setBackground(Color.green);
	add(to);
        to.setTransferHandler(new TransferHandler("background"));
    }

    public static void main(String[] args) {
        JFrame aFrame = new JFrame();
        aFrame.setSize(100, 300);
        aFrame.setContentPane(new ColorDnD());
        aFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        aFrame.setVisible(true);
    }
}