customizeSegment method
To customize each segments.
Implementation
@override
void customizeSegment(ChartSegment segment) {
  final int index = segment.currentSegmentIndex;
  final bool isBull = closeValues[index] > openValues[index];
  final Color color = isBull ? bullColor : bearColor;
  final Color? segmentColor = pointColorMapper != null &&
          pointColors[segment.currentSegmentIndex] != null
      ? null
      : color;
  updateSegmentColor(segment, segmentColor, borderWidth,
      fillColor: segmentColor, isLineType: true);
  updateSegmentGradient(segment);
}