I've just switching work laptop to grayscale mode. Done partly to stop apps stealing attention with bright colors, partly to test for accessibility day-to-day. Most difficult thing so far has been viewing diffs; I have to pay more attention to the +/- at the start of the line. Most other stuff has been surprisingly ok. Apps generally look a bit simpler. Video calls feel like watching a movie from the 40s.
For macOS the setting is in System Preferences > Accessibility > Display > Use grayscale
For Android it's available at night with 'Digital Wellbeing' app, but I had problems with that in the past so don't trust it. Looking for alternative.
On Windows it can be toggled with Ctrl + Win + C (Or search for 'Color Filter')