How to change chart color of "Previous data" on Diff Charts?

[manzolo]

The default data color of "previous data" on diff charts is #eeeeee.
With $chart->getOptions()->setColors(['#xxxxxx']); i can set colors of oldColumnChart and newColumnChart.
Is there a way to set color of diffColumnChart?
https://github.com/cmen/CMENGoogleChartsBundle/blob/master/Resources/doc/diff_charts.md

EDIT:
I found this workaround:
$('rect[fill="#eeeeee"]').each(function () {
$(this).attr("fill","#anothercolor");
});
But i don't like it...

[cmen]

It seems it is not possible to configure "previous data".
Nothing in Google documentation: https://developers.google.com/chart/interactive/docs/gallery/diffchart

Other people have the same problem: google/google-visualization-issues#2552