Currently running UI 5 Upgrade and noticed that previously when my device was scheduled to 'do not disturb' and the screen turned off colour mode (ie became monochrome) the Upgrade to UI 5 no longer does this.
Tried searching all over settings but cannot find this setting as it seems to have been removed.
Search for 'modes' in your settings menu, this was previously called bixby routines but has changed to modes in one ui 5. Set up a sleep routine and you'll get the option to turn greyscale on.