Paints will run you into the rabbit hole of finishing processes with layer lines. Also most paints are formulated for adhesion to steel. This has to do with the anticipated rate of expansion due to temperature. ABS is typically used for plastic automotive parts like trim and bumper covers, mirrors, door handles, etc., because it has the closest temperature expansion properties to steel.

In automotive painting, ABS can accept most of the same finishing processes as panel work, while any other types of plastics require an adhesion promoter layer. The most common adhesion promoter in the USA is called bulldog. It can be bought in spray cans but as of 15+ plus years ago when I owned my auto body shop, the spray cans are terrible at inconsistent spattering and useless unless you know some very special techniques that involve pro paint spraying equipment.

With PLA, you will likely have success painting with model paints. Most of these never fully cure like an automotive class 2k catalyzed hard surface finish. The soft state of these enamel paints creates its own unique issues. Any kind of higher end paint is likely to have adhesion issues due to handling and temperature fluctuations where the PLA moves differently than the overlying shell and the tension eventually breaks the mechanical bond of the coating. It is an option though. High level finishing with layer lines is a very intensive process to do at a high level. I actually prefer a similar process in total using ABS and polishing, but that is a whole different can of worms. A little vibrating pen sander makes a big difference when it comes to sanding. I used to tell people automotive paint and body repairs are 99.999% sanding and prep. It is impossible to really convey the amount of sanding required for perfection, but this is where real perfection happens and there are no shortcuts.

Alternatively, if you get a bunch of filaments, and you do a lot of prototyping, just use the oddball colors for iterative work on designs. This is what I do. Filament colors is likely both the most cost and time effective option if you are okay with the look of layer lines.