I was just talking with Seth Rochford, busy putting paint and polyurethane in our not-quite-complete carriage-house. I mentioned some of my longer-range thoughts about the geo-exchange heating system (which may finally be turned on this week, yay!) and he replied that no matter what happened with that kind of technology, he figured he'd still be using brushes, slapping chemicals on walls. I disagreed.
Start from the fact that the surfaces will all be recorded in 3D modeling programs; I tend to take this for granted. That's easy. So the "painter" will stand with the customer in a virtual space, using graphics better than today's best, choosing colors/textures that will go with each other under various lighting conditions. At the end of this process there will be no more decisions to be made.
We now have a robotic framework which translates the virtual coordinates into physical locations; this can range from a robotic ladder which moves itself along, to a self-driving rented truck which drives to the indicated address and unfolds itself into a framework which covers the building (whether outside or inside). In either case, the framework has tracks. Now look at the inside of your printer, where the print-head rides on rails. (A variety of design options is available here; consider the series-of-2D-printings method for achieving 3D printing, as in Evil Mad Scientist Laboratories' CandyFab: "The X and Y axis motion control systems are based on belt drives and quadrature-encoded motors recycled from two old HP plotters, a large one and a small one".) In any case, for each point in the chosen virtual surface, there is some time-range within which that point can be reached by a robotically wielded "brush". The rest is software.
An alternative to the physical framework is a swarm of mini-robots which crawl or fly over the surface, printing as they go. An even more radical alternative would be mini-(or micro-, or nano-)bots which are the right color/texture, or can change, and which simply go to the right place and form a skin. Suppose that the nano-technology used for this is the nanotech getting most funding right now, namely human DNA: if your paint is made of modified human cells, and if it has a neural component to guide self-repair or calls for replacement, will it have rights?