Open the Reason Home app on your smartphone. In the Home screen, tap the card that's corresponding to a device.
On the next screen with the top line showing the device name, tap the Settings (gear) icon in the upper-right corner.
On the next screen ("Settings"), tap the Night Mode toggle button to turn on/off the option. When turning on the Nigh Mode, please set the start and end times defining the period during which the clock face and the Action button light on top will be turned off.