Diagnosis
This is typically caused by external light pollution or a dirty lens/sensor. Even a small amount of ambient light (a streetlight, digital clock, power LED) can wash out the infrared and create a grainy, greenish image.
How to Fix It
First, clean the camera's lens and the surrounding black IR lens cover with a soft, dry microfiber cloth. Fingerprints cause weird reflections. Next, check the camera's immediate environment. Are there any small light sources in its field of view? Even a charging brick's tiny LED can cause this. Try to eliminate or block those lights. In the Wyze app, you can also try toggling Night Vision between 'Auto' and 'On' to see if one setting handles the ambient light better.
If That Didn't Work
The IR cut filter inside the camera, which switches between color and night vision, might be sticking or malfunctioning. Try power cycling the camera. If the problem is consistent and your room is truly dark, it could be a hardware fault.
Heads Up
The night vision on these cameras works best in total darkness. They're not designed to mix IR light with visible light, which creates the grain and color cast.