myButton.addActionListener(e -> {
    Card[] cards = selectThree();
    highlightBorders(cards, Color.RED);
    int delay = 1000;  //  timer delay in msec
    // create a Swing Timer
    javax.swing.Timer timer = new javax.swing.Timer(delay, evt -> {
        // action we want the timer to perform
        highlightBorders(cards, Color.WHITE);
    });
    timer.setRepeats(false);  // it performs its action only once
    timer.start();   // start up the timer
});