Reece, check these examples: https://mydemoversion8-sandbox.mxapps.io/p/appdemo/gridcellstyler and https://forum.mendix.com/link/questions/94594
Hi Reece,
As Tim mentioned you will have to mention the Colum name, I have also implemented CellStyler for my Datagrid.
For your Ref:
In your SCSS file you can just write the color and add your style with the Class name you have given in the widget.
Good Luck !!