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