If you recently upgraded to a galaxy S10 model you may have come across a greyscale issue where your phone seemingly turns the screen black and white for no apparent reason.
It could be this is related to your do not disturb settings.
Samsung introduced "wind down" to help you with time away from your device.
If greyscale is turned on and it's not because it's been switched on in the accessibility settings then search "wind down" in your settings search bar (not the app search bar).
Under wind down you can turn off greyscale and return your phone to glorious amoled colour.
I went to 2 telstra stores and got a replacement phone before I discovered this no one seemed to know this option existed.
Hopefully this saves you some time.