Problem with getting buttons to automatically turn off by using a timer

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Java

Eclipse

Hello there am creating a game on Java and I am struck on how I would automatically change my buttons to a different colour

My code is below...


// panel center

for(int x = 0; x < 12; x++)
{
JButton btnx = new JButton();
btnx.setBackground(Color.GREEN);
btn[x] = btnx;
//btn[x].setText("HI THERE"+(x+1));
btn[x].addActionListener(this);
pCentre.add(btn[x]);
}

cPane.add(pCentre,BorderLayout.CENTER);
}

What I have tried:

I have to set the background color to NULL then create timer which would change the button color every 3 seconds