Since AC12, Graphisoft introduced a new kind of Attribute called Building Material, where you can set intersection priorities for each individual BM.
After defining the BM priority, also check if the Layer Intersection Group Number is the same for all involved elements.
Regarding Wall colors, you can set many other things, including cut fills in the Building Material Dialog Box. Also check if any Graphic Overrides may be interfering in your floor plan.
About turning of composites in sections: If I understand you correctly, you probably need to create a new GO Rule and set a style to cut fills and background fills.
Hope this helps.