Just imagine the amount of work for pakset maintainers!
Potentially no work at all, like most additions on the graphics side. You simply would not be required to use it, if you are fine with the current system. There is no need to abandon the special-color-code if night-images indeed get added.
Though is it really feasable to add "night" as another complete image, like seasons and rotations? It's no problem for street lights and vehicles, but it might be a burden for buildings. After all, they already may have 8 rotations and 5 seasons, so you could end up having to create 40 new images just for that one building to use better lights.
Even worse, sometimes it's the same building with a variety of colors or different accessory. All of those slightly different versions would have to be duplicated for a night image. The creation process can be automated, but you'd still end up with a lot more wasted storage - in the games memory as well.
I'd like to propose "light" as an extra image layer, similar to frontimages, but only appearing at night and of course not affected by night-screen-tint. This would allow to use one "lights" graphic for several buildings that have their windows in the same positions; or reuse the same headlights for several vehicles, etc.
These would not replace special colors, however, and rather accompany them. The streetlights vladki used would still have the special color where the lamp is, but the glow would be in an extra layer. Using such a system, we could allow the player to opt out of these "advanced lights" and no light layers would be rendered at all. - just in case it would be too much for older computers.