libGDX : Paint And Remove Color From Actor with touchDragged

I created two-dimensional array of Button actor, then I added new ClickListener() {
touchDragged } as the following code:

buttons = new Button[3][3];

for (int row = 0; row < buttons.length; row++) {
    for (int col = 0; col < buttons[0].length; col++) {

buttons[row][col] = new Button(drawable);

buttons[row][col].addListener(new ClickListener() {

                @Override
                public void touchDragged(InputEvent event, float x, float y, int pointer) {
                    for (int row = 0; row < buttons.length; row++) {
                        for (int col = 0; col < buttons[0].length; col++) {
                            if (buttons[row][col].isOver()) {
                                buttons[row][col].setColor(Color.GREEN);
                            }
                        }
                    }
                }
   }
}

the code inside touchDragged method if the buttons isOver the buttons colored GREEN (it works fine) as shown in image

Now, How can I remove Color.GREEN i.e. (Color.WHITE) from buttons in the same calling touchDragged method, I mean undo GREEN to WHITE ??

this image clear my question :

like Alphapetty Game from king company, if you know it .

Sorry, For bad English