What colour for cardboard parts?

[N. W. Perry]

If you only want the "correct" base material, have you tried simply using Canvas White or Cream?

It's obviously not correct, but it should give a somewhat similar, "fiber-y" feel. A bit similar to how you can use Rubber colours to create the miky variants of Transparent colours for parts cast in PP/PE like 30093.

Yes, canvas is what I'm using as a fallback. You need Canvas Tan for raw cardboard, though it isn't a perfect match.

But for rendering in Studio, the only option appears to be rubber, at least until I learn how to create new materials.