I am running along using my happy Windows 10 PC. I was trying to do something fancy keyboard hotkey and all of a sudden all my apps on all monitors went black and white (a.k.a. gray/grey grayscale/greyscale... kinda Ansel Adams photo looking). I am a keyboard guy. I really like hotkeys, but sometimes there is a misfire where my fingers don't exactly do what my brain told them to do. I look at my screens, one eyebrow raised. What just happened. Did my video card just crap out? Maybe a loose cable? But why would that cause both monitors... hmm. What have I done. Do I need to reboot? Before doing anything else I hit the Windows key and type "grayscale". Hmm... what is this? "Turn color filters on or off". Clicking this brings you to settings. Here you learn that we have added a hotkey, CTRL+WIN+C to turn on and off this option. This is not the key sequence I was attempting, but it was really close. High five to the person who made sure the grayscale would show this setting. Just thought this might help a fellow keyboard hotkey user.