private @Nullable Color getColor(MouseEvent event) {
      Couple<Integer> pair = pointToCellCoords(event.getPoint());
      if (pair != null) {
        int ndx = pair.second + pair.first * 10;
        if (myRecentColors.size() > ndx) {
          return myRecentColors.get(ndx);
        }
      }

      return null;
    }
private @Nullable Color getColor(MouseEvent event)