When considering the colors of the reconstructed Tantive IV set in RotS, even if everyone involved in it was sincere in faithfully recreating it, it, like everything else we see in the PT that is from the OT, would probably have been done under the instruction and mindset that this is when the ship was fairly new. In-universe, the ship has 20 years worth of grime, build up, abuse, and maintenance compromises between then and how it ends up looking by '77 Star Wars. So, really RotS is no reference other than that with the lighting technology used “20 years earlier”, the walls of the fresh and well maintained ship were intended to appear white to start with.