For your reference, please take the following steps:
1. Go to the [Mi Home/Xiaomi Home] APP >> select [Device card] >> tap [...] at the upper right corner >> select [Camera settings] >> tap [Night vision function] to enable it;
2. You can choose to turn on or off [Night vision function], [Black & white night-vision mode], and [Smart full-color mode].
Note:
1. Black & white night-vision mode:
The night-vision light is enabled with infrared fill light to deliver black and white images;
2. Smart full-color mode:
After the night-vision light is turned on, the full-color mode will be enabled automatically with the fill light on if a human body is detected.