Meant to be red from the factory, but 2nd fl were made after Renault got their hands on nissan and started making them even cheaper than they were, so it fades like hell. Maybe other techniques of restoring faded plastic (peanut butter etc) might bigger it back to red? Otherwise, standard prep and paint, or a sharpie marker, depending on how much you can be bothered
Edit: realised you weren't asking why it happens, been a long day....