Tonight I sat on my studio iMac to make some music. Suddenly by screen lost colors and turned black and white, preceded by some flickering. I first thought it was Chrome's fault as it updated to version 73 which brings the dark mode to macOS devices but it wasn't.
After a restart the color went back. But the problem persisted. After some investigation I found out that this is a macOS accessibility feature you can turn on and off. After I toggled that setting everything worked stable.
But what was the cause for it? I just connected and used a new hardware on this machine, the Native Instruments Komplete Kontrol M32 keyboard. I accidentally turned on the accessibility feature by hitting SHIFT + IDEAS on the device which also brought up the voice assistant - my keyboard started to talk to me with a weird German accent, telling me the settings I am going to tweak with all these knobs. I suspect this software to also set additional settings in that area that caused my screen problem but of course I am not sure.
If you ever experience the black/white problem just try to toggle the settings once. Goto system settings, accessibility, display and uncheck/check the grayscale settings once.