how feasible / advisable is it to paint a Kodiaq's black bumper and side skirt plastics to match a car's colour ? 

I have painted plastic before but you need to use difficult surface primer (not standard primer), then an undercoat (ideally approx colour), before applying the coloured top paint.   If you have pearlescent type paint then will probably need a clear coat too.

 

If you try and shortcut it and just go to top colour, paint won’t key to surface properly, or will apply too much paint to try and change colour, and get a poor eggshell type finish.

 

So not a quick job to do properly.

 

I’m no expert, but I would have thought that if properly prepared and primed, it should be possible.

 

Why you would want to, however, is another matter entirely - but each to their own 😁.

I had this done a few years back on my Audi A4 avant at the time.. no issue with for years after.. Are you doing it yourself??