public void setTrackColor(final TileColor COLOR) {
        if (null == trackColor) {
            _trackColor = COLOR;
            fireTileEvent(REDRAW_EVENT);
        } else {
            if (!trackColor.isBound()) {
                trackColor.set(COLOR);
            }
        }
    }
Defines an optional node that can be used in combination with the
CustomTileSkin.
@param GRAPHIC
src/main/java/eu/hansolo/tilesfx/Tile.java