Anyone who has tried using grayscale or any of the other color correction modes has probably experienced the situation where you can't get it to deactivate once you've turned on the setting. I searched for other threads about this and read that it is some kind of bug with android but no one had a real solution. I use grayscale as a permanent setting on my phone, but for taking photos or looking at photos I like having the ability to quickly toggle the setting without having to reset my phone. I seem to have found a solution to this problem.
If you have a color correction mode turned on, any of the color correction toggle shortcuts will work if you have the Night Light setting turned on as well. For some reason the color correction toggles function as intended if the night mode setting is currently activated. So if you have something like grayscale activated and want to turn it off to take a photo or something, you just toggle off color correction, then toggle off night light, and you are back to full color phone. Reversing it is as easy as toggling both back on in either order, or just turning on color correction if you want to leave night light off until you need a full color phone again.
I use the grayscale setting on my phone in conjunction with other settings as a way to make a minimalist style phone, so having night mode activated all the time isn't really a big deal for me. However, I can understand why this wouldn't be a viable solution for many. Just thought I would put this out there for anyone who has run across this issue or might do a search on the forums for it in the future.