OPAL material NODES here + tutorial on YOUTUBE - Tutorials, Tips and Tricks - Blender Artists Community
80 Level Digest: Learn How to Create Complex Shaders in Blender
Blender Illustration Shader - Eevee Live Lighting Tutorial - YouTube
This is a free Diffuse BSDF Shader guide to help Blender users, extract from one of my free PDF guides and YouTube tutorial below, hope you find it useful :) : r/learnblender