customizeSegment method
Changes the series color, border color, and border width.
Implementation
@override
void customizeSegment(ChartSegment segment) {
  final BarSegment<T, D> barSegment = segment as BarSegment<T, D>;
  updateSegmentTrackerStyle(
    barSegment,
    trackColor,
    trackBorderColor,
    trackBorderWidth,
  );
  updateSegmentColor(barSegment, borderColor, borderWidth);
  updateSegmentGradient(
    barSegment,
    gradientBounds: barSegment.segmentRect?.outerRect,
    gradient: gradient,
    borderGradient: borderGradient,
  );
}