code: function (d, chart, series) {
              var returnFill = 0;
              if (series.c !== null && series.c !== undefined) {
                  returnFill = d.fill;
              } else {
                  returnFill = chart.getColor(d.aggField.slice(-1)[0]).fill;
              }
              return returnFill;
          }
docs: Calculate the fill coloring for series