[Solved]-highcharts treemap heatmap level2 color turning black-Highcharts

As you might have seen, the GitHub issue has been fixed and closed. Use a version of Treemap from 4.1.6 or above, and you should not have this problem.

Alternatively it is possible to add the following code snippet after loading Highcharts and before creating the chart:

Highcharts.seriesTypes.treemap.prototype.getExtremesFromAll = true;