Once done, re-start the presentation services, clear the browser cache and verify the changes.
I have tested this on 188.8.131.52.6 and it works perfectly fine!
Also, to test if promptOperatorLabelNarrowView class is indeed affecting the color of the operator, try below on any of your dashboard where you have between operator:
- Edit Dashboard and add a text object.
- Select the option for 'Contains HTML Markup' and the below code:
- Save the dashboard and click on Run.
- The operator color now ideally should be Black.