I've bound toggling greyscale on/off to pressing the lock-button 3 times, makes it very easy to switch back/forth when you need it, but still be able to leave it greyscale most of the time.
I do this too but often forget to turn it back on when I need it off (e.g. for maps or for looking at a picture)
I do this too but often forget to turn it back on when I need it off (e.g. for maps or for looking at a picture)