Just a heads up, since it was on my todo list for a while, that I’ve just (re-)implemented support (it used to exist, but I did a rewrite) for BlenderBIM importing object-level surface styles.
BlenderBIM’s import also distinguishes between an import of object-level and material-level surface styles. To my knowledge, this is the only BIM program which does this. So later on when you click on the object to see its colour properties, you can see whether it was assigned via material or assigned via object.
@Hans_Lammerts - see a screenshot of a portion of your model you sent me below, with colours!
I will mention that this Allplan IFC file seems to have a lot of identical colour and surface definitions for the exact same colours. Blender can handle this, but it results in a bloated and inefficient IFC file, and unless Blender compensates, it means that the import takes longer and creates more data. If Allplan doesn’t fix this, a workaround is to run the IFC through an IFC optimiser. I think Solibri has one in their product portfolio.