private void writeObject(ObjectOutputStream stream) throws IOException {
        stream.defaultWriteObject();
        SerialUtilities.writePaint(this.firstBarPaint, stream);
        SerialUtilities.writePaint(this.lastBarPaint, stream);
        SerialUtilities.writePaint(this.positiveBarPaint, stream);
        SerialUtilities.writePaint(this.negativeBarPaint, stream);