private void adjustBackgroundColor() {
        Color color = gradientLookup.getColorAt(getSkinnable().getValue() / (getSkinnable().getMaxValue() - getSkinnable().getMinValue()));
        background.setFill(new LinearGradient(0, 0, 0, size,
                                              false, CycleMethod.NO_CYCLE,
                                              new Stop(0, color.deriveColor(0, 1, 0.8, 1)),
                                              new Stop(1, color.deriveColor(0, 1, 0.6, 1))));                        
    }