public Paint getTickLabelPaint(Comparable category) {
        if (category == null) {
            throw new IllegalArgumentException("Null 'category' argument.");
        }
        Paint result = (Paint) this.tickLabelPaintMap.get(category);
        // if there is no specific paint, use the general one...
        if (result == null) {
            result = getTickLabelPaint();
        }
        return result;