mm (but I know that all websites ask, so maybe TBD and some metadata if possible. I'm yet to read the standard for the CT primitive.)
just ignoring color for now.
I mean that flat faces can be represented using one plane and a bunch of lines. The round is only for what's actually curved in OpenSCAD language.
BTW, I never was able to import an STL into FreeCAD successfully. Firstly, the import process cannot figure out inside and outside correctly. And "repair" step either does nothing or makes it worse. Secondly, I cannot do anything with the result. Yes it sits in the tree and UI kinda displays it in 3D, but nothing else is possible. It all goes back to my fundamental inability to make FreeCAD do anything, I'm sure.