What works for me is removing the antecedent completely by charging my phone in another room at night.
Now the battle is easier: Decide once a day to put it there, and track how many days you succeed.
For me that's a lot easier than having it in my pocket, where the Internet is always a couple lazy taps away. Now I at least have to walk to it if I want it, and that often "breaks the spell."
I finish work and chores hours earlier when my phone is charging in another room, without consciously doing anything else differently.
It really makes me want a 1980s-style cellphone with no screen and big physical buttons.
OneSec [1] is the only one that worked for me. It's quick enough that I'm not tempted to disable it, yet annoying enough that makes me think twice if I really want to open app X for the third time today.
Also it's just a polite nudge, rather than a full block, or condescending messages saying "you've hit your time limit for today" (that make you feel bad and make you want to immediately disable the thing in the first place).
Wish parental controls were designed with the same principles.
Black and white kills the dopamine cycle and brings color back to your real life.
Or you're talking about literal black-and-white, as in 2 colors no grey?