import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import javax.swing.event.*;
class Yanse1
{
   JFrame f=new JFrame("两种颜色");
   JPanel p1=new JPanel();
   JPanel p2=new JPanel();       
   GridLayout g=new GridLayout(1,2);
Yanse1()
  {
   p1.setBackground(Color.BLACK);
   p2.setBackground(Color.white);
   f.add(p1);
   f.add(p2);
   f.setLayout(g);
   
   Yanse yan=new Yanse();
   Yanse2 yan2=new Yanse2();
   p1.addMouseListener(yan);
   p2.addMouseListener(yan2);
   
   f.setSize(300,300);  
   f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
   Dimension d=Toolkit.getDefaultToolkit().getScreenSize();
   f.setLocation((d.width-200)/2,(d.height-120)/2);
   f.setVisible(true);  
  }   
public class Yanse implements MouseListener
{
   public void mousePressed(MouseEvent e)
    { }
   public void mouseReleased(MouseEvent e)
    { }
   public void mouseEntered(MouseEvent e)
     {  
      p1.setBackground(Color.pink);
     }
   public void mouseExited(MouseEvent e)
     {       
      p1.setBackground(Color.blue);
     }
   public void mouseClicked(MouseEvent e)
     { }
}
public class Yanse2 implements MouseListener
{
   public void mousePressed(MouseEvent e)
    { }
   public void mouseReleased(MouseEvent e)
    { }
   public void mouseEntered(MouseEvent e)
     {  
      p2.setBackground(Color.yellow);
     }
   public void mouseExited(MouseEvent e)
     {       
      p2.setBackground(Color.red);
     }
   public void mouseClicked(MouseEvent e)
     { }
}



public static void main(String args[])
   {
    Yanse1 y=new Yanse1();
   }       
}

这部分复杂但不难

GUI编程，你学会了，好样的，继续努力。