From the little I have played with the paint tools all I can say is most of them seem really clunky.
For what your photos appear to show I would consider using the cut tool to slice them horizontally at all the heights where you want to change color. Use the into parts option.
That would give you a crepe load of parts, but, it is fairly easy to multi-select them and assign a filament to them.
Edit: After playing with this myself it doesn’t do what I expected. When cutting I thought it would create separate parts for volumes that became disjoint but it doesn’t. Maybe your CAD program if you use one can do it.