Changing background color of selected cells in pivotview

Hi,

I use a Angular / Javascript pivotview with multiple cells selection enabled. 

How can i changed the background color of the selected cells ?

     this.pivotGridObj.gridSettings.allowSelection = true;
     this.pivotGridObj.gridSettings.selectionSettings =      { mode: 'Cell', cellSelectionMode: 'Flow', type: 'Multiple' }

I tried to access the grid object directly, but this is always undefined.

  if (this.pivotGridObj.grid !== undefined)
          this.pivotGridObj.grid.queryCellInfo = this.customiseCell;