Yeah, I thought about doing this...but then I realized I've already cut back the behaviors this is trying to control, or never adopted them in the first place (I was a late smartphone adopter and have had most notifications disabled for as long as I've had one).
This grayscale challenge seems more to help phone addicts break their habit, but seem to do much if you aren't one and/or don't use social media apps.
Don't get me wrong, I really like the idea. I'd probably do it if I could selectively enable color only for certain utilitarian apps, like my Camera and photo-viewer.