Simple Background Color

How do i set the background color in this code. I am new to Java as you can see.

Thanks!
import java.awt.*;
import java.applet.Applet;

public class StopLight extends Applet {
      //setBackground(Color.blue);
      public void paint(Graphics g) {
            g.drawLine(150,100,150,200);
            g.drawLine(151,100,151,200);
            g.drawLine(152,100,152,200);
            g.drawLine(153,100,153,200);
            g.drawLine(154,100,154,200);
            g.drawLine(155,100,155,200);
            g.setColor(Color.black);
            g.fillRect(133,10,40,97);
            g.setColor(Color.red);
            g.fillOval(140,15,25,25);
            g.setColor(Color.yellow);
            g.fillOval(140,45,25,25);
            g.setColor(Color.green);
            g.fillOval(140,75,25,25);

      }
}