See the images. First one is how it looks, second one is how I want it to look.
So far, it seems to me that this can be achieved two ways:
a) using the paint tool
b) overriding by category or element
The problems with these methods:
a) If the slab changes shape (let's say, it goes from a rectangle to a pentagon), the user needs to find the new edge face in 3D and paint it. Also, it's a lot of painting on projects that are large, and a lot of work for projects in flux.
b) Every time you make a new view, you need to be sure to apply properties or a view template that deals with this. In the case of walls of different material types (and corresponding graphical colors), it'd have to be element-specific.
Either in object styles, material properties, or type properties, I'd want it that if I draw the wall or floor in question, it shows up with all faces the same color, in Hidden Line view, without needing to use the paint tool or V/G, for the reasons listed above.