How to have different colors/textures on bottom and top side of a Plane?

[hofk]

@hofk

I now have a form that is simple and practical for me. The shader is a black box and can be replaced by another variant if necessary. (not by me )

I wanted to use this two-color display in a current project and found that the pen @prisoner849 no longer works. What works is the copy in the Collection of examples from discourse.threejs.org :
DoubleSide(gl_FrontFacing)

However, I get an error when customizing my above example SimpleDoubleSide(gl_FrontFacing) to r160:

THREE.WebGLProgram: Shader Error 0 - VALIDATE_STATUS false
. . .

I assume there have been breaking changes to r112?