Buttons change color, but I need them to stop when I click them

Cloud Berries :

this is my first time posting a question here. I'm new to java and currently taking a course on it. This is the assignment: "Modify your button GUI program so that the buttons change color about every one second unless they've been pressed." ...that's all the instructions I was given. haha its like nothing!

So I know right now that when the button is clicked it turns white and stops changing. Technically that satisfies the instructions given, right? I don't think thats what they want though...Plus I'm just changing the opacity, so it's still changing color, you just can't see it, right? So what I wanted to know is if there was a way to maybe stop the button from changing color but keeping the color it already has like freezing it, instead of turning it white? I have a static JFrame jf, static Boolean pressed outside main and all the proper imports. My getColor() function just returns a random color. Thanks for the help/advice!!

public static void main(String[] args) { 
        jf = new JFrame("Homework 2");//constructed
        jf.setSize(400,400);//sets window size
        jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);//closes program
        jf.setLayout(new GridLayout(2,4));
        ArrayList<JButton> buttons = new ArrayList<JButton>();//array of button
        pressed = true;
        for(int i=1; i <= 8; i++) { //creates 8 buttons
            JButton jb = new JButton();
            jb.setText("Button " + i);
            jb.setOpaque(pressed);
            jb.setBorderPainted(false);
            jb.addActionListener(new ActionListener() {
                public void actionPerformed(ActionEvent e) {
                    JButton theButton =  (JButton)e.getSource();
                    theButton.setOpaque(!pressed);//makes it white if it has been clicked
                }
            });

            buttons.add(jb);//add the button to the array
            jf.add(jb);//adding to frame
        }
        jf.setVisible(true);//makes the window appear
        while(true) {
            for (JButton button : buttons){
                button.setBackground(getColor());//change colors
            } 
            try {
                Thread.sleep(1000);//unless 
            } catch (InterruptedException e1) {
                e1.printStackTrace();
            }
        }

    }

Andrew Thompson :

To remove (stop) the button from further color changes, remove it from the buttons array list when an action is performed.