Yeah same. In my simple mind I liken modern apps (esp. social apps) a bit like a casino - there's so much colors and "things going on" that it just feels a bit too intense for me over time. And color was one of the few app-configurations (along with muting notifications, adding Screen Time, and maybe complete uninstallation) that I had control over.. at least on the desktop web you can have extensions block some stuff for you. I tried greyscale mode on desktop too btw but to ruin the surprise for you - it SUCKED! :-)