I tried this. One week in, I got used to grayscale as well and my screen time was back to the baseline (maybe only marginally affected). After nearly a decade of trying these tricks, hacks, and gamified interventions, it’s clear to me why they rarely work: they fixate on the symptom (screen time, social media use) rather than the underlying problem. Your mind craves to feel engaged/challenged in something. So, the actual problem is finding meaningful activities to replace your empty screen time, which isn't necessarily easy.

If you want to reduce your screen time, the boring old discipline is much more sustainable approach. Put the phone down and replace it with a book, or puzzles, or hobbies, or time with people.