If you are lucky enough to still have the fascias and bumpers in unpainted black plastic, the small scratches will be almost invisible as you know.
In this case, however, over time the sun will tend to cook the plastic graying this part.
To remedy this unsightly effect that the car ages a lot, there are two solutions, one to replace the damaged parts, or buy the special blackener product for plastics which, in addition to restoring the black color, protects them over time from the sun's rays . p>
This product is not very well known and you will need to look for it in some well-supplied auto accessories.