Sorry this is a silly problem :/ which I can't resolve.
I geuss some light "diffuse" through the hair and leave the skin a green-ish tint, which is undesirable. Can I somehow let skin material and hair material don't interact with each other?
below picture is the node setting for the skin material.
below picture is the node setting for the hair material + hide hair, as you can see, the green tint is gone.
ps. I thought the outcome would look better but it literally looks like an inflatable doll. Epic fail.
