GitHub - Philipp-Seifried/Blender-Normals-To-Vertex-Color: Simple Blender 2.8x addon that copies a selected object's normals to its vertex colors. Useful for some shader tricks.
How to use 'Set Vertex Colors' properly? - Blender Stack Exchange
Dirty Vertex Colors | Barbara Seaton
Small Blender Things: Transfer vertex weights to vertex colors and vice versa
Blender addon - Bake to vertex color - BlenderNation