The Subsurface Scattering in Principled BSDF is a bit confusing:
- Where can I find some material presets?
- What is the difference between Scattering Color and Radius?
Values of around 0.01 are normal, since you're scaling from meters to milimeters
Scale the radius down using the Subsurface slider
(just drag it into image editor and colorpick the values)
Source chart from Pixar. Original paper here.
Sources
Link -
Henrik Wann Jensen, Stephen R. Marschner, Marc Levoy and Pat Hanrahan: "A Practical Model for Subsurface Light Transport". SIGGRAPH'2001.
An Introduction To Real-Time Subsurface Scattering, Stanford Dragon - Stanford University Computer Graphics Laboratory, Subsurface - Arnold Renderer, Subsurface - Substance Painter, Subsurface - Renderman