The device has a light signal ring at the top that indicates the status of the air in the room through different colours. As the manual explains, blue means good air quality, yellow means medium quality, and red means poor air quality.
The upper ambient light ring is not related to UVC light. The UVC light is hidden inside the device avoiding exposure to the user for their safety.
Whenever the rear cover of the equipment is opened, it is recommended to disconnect it from the mains to avoid exposing yourself to UVC light or its moving parts.