ngx-datatable rowClass is not working

The problem is that your .row-color is scoped to test component. You need to prefix it with /deep/ to break encapsulation:

/deep/ .row-color {
  background-color: green;
}

Alternatively, you can use ViewEncapsulation.None to have your CSS rules go around the app.

Or you need to put this rule somewhere in your global app styles (not bound to any one component).

Here's a working Stackblitz.

What ViewEncapsulation.None does means something like this:

Any css you write will be applied not only on your component, but to the whole context (page). If you Inspect element, you'll see on angular components that you have things like <span _ngcontent-c15>...</span>. So all the stuff on your component, angular marks with the attribute _ngcontent-c15 (or similar). Then all the styles from your component are not simply span, but rather span[_ngcontent-c15]. So if you paint your spans red, it won't leak to other components (they'd be e.g. _content-c16). ViewEncapsulation.None removes that attribute from your component CSS so it's valid all over the page.

Make getRowClass() a proper function and it will work:

getRowClass(row): string {
  return 'row-color';
}