In UE4.26 path tracing does not work with SSS Shaders , that's why you see green.
In UE4.27 it does work with SSS but you will have some issues with the eyes. ( you have to deactivate eye occlusion )
It is not CC3 related , with the upcoming UE4/5 updates it should work , it is still experimental.

Path Tracing in UE4.27  :

Yeah I have. I just don't know if I have missed anything. 

Ive never seen this before, are you using the auto set-up plug-in?

Hi, 
I've been experimenting by importing CC3 characters into Unreal Engine 4.26.2 and I wanted to try out Path Tracing. But, when I turned that on, the character(s) from CC3 turn green! 
I don't know what is going on or what I am doing wrong. Does CC3 support Path Tracing for CC3 characters for Unreal? 
I've turned on Ray Tracing and it's on DirectX12.