I have this fiddle
https://jsfiddle.net/mtzhexqg/
Close to the bottom, I have this line…
//cellProperties.renderer = negativeValueRenderer;
With this, the column number formatting works.
If you uncomment this line you will see that the coloring works as expected, but I lose the number formatting.
Is there something I need to do to maintain the number formatting in the renderer other than add to the cells classList? Or a better way?