Hi Bebop,

You could try finding the source of the green light by turning off first individual lights, then global illumination, reflections, and so on... if you find which actor or setting is causing it, then you might have a better idea of how to fix it and how it is related to the video card.

Also, it could be that Unreal 5's Lumen hardware ray tracing is used in different ways on those video cards or produce different visual behavior. You can turn off the Hardware Ray Tracing in Unreal's Project Settings:

And you can also ask the same question on Unreal's forum, maybe somebody encountered the same issue there: https://forums.unrealengine.com

Warmest regards,