All skin is slightly translucent, and color/tones forms a gradient across the surface of the skin. Your upper cheeks and forehead are usually slightly reddish, and the chin/neck are slightly bluish.

People only turn yellow if they have kidney or liver damage. However, some distinctive features like Lucy Liu's natural freckles are tough to draw right.

We looked around a lot for a procedural texture/shader to help make the project characters look less sickly, and please also consider supporting the persons work if you are able:

https://kuhantilope.gumroad.com/l/ultimate-skin

Best of luck =3