Changing colors after raytracing
What you describe is essentially a deep raster. Most modern renderers implement this in fact it is implemented in several ways. There are even sopecific technical positions that rely on this technology in form of lighting, color grading and compositioning artists

The first technique is multipass rendering which is basically just this dumping of render data out of the renderer for fast defered rendering.  All rendering engines on the planet can do this, though all do not implement dumping it out of one render, most do however). What you then do is you integrate these dumped buffers in a compositioning app (Nuke, Fusion, maybe even after effects, you can even do this in photoshop) where you can do final tweaks and changes. This is a very old idea and has been used for more than 30 years. It has certain drawbacks bit overall this means you night be able to pull off even calculation changes that would be too costly to do with a re-render. So color of objects

Many systems also support interactive sessions that cache the computations, in what is essentially a deep raster. This way its possible to recalculate not only color but even the position, decay of individual lights at interactive speeds. The most modern ones of these are frankly quite sophisticated and can also issue the renderer to rerender in background. Animation studios have lots of people working on these to make them better.

You can even use this trick to change camera position for the second stereo camera without recomputing your scene.