Slick2d java game crashing when I setBackground();-Collection of common programming errors

I’m using slick2d and in my Java application. In my render method I use a method called changeBackground();

@Override
public void render(GameContainer gc, StateBasedGame sbg, Graphics g)
        throws SlickException {
changeBackground(g);
}

changeBackground();

public void changeBackground(Graphics g) throws SlickException{
    Thread.sleep(500);
    g.setBackground(new org.newdawn.slick.Color(0, 255, 0);
    Thread.Sleep(500);
    g.setBackground(new org.newdawn.slick.Color(255, 0, 0);
    changeBackground(g);
}

When I run my application the game crashes.