An unliveried chauffeur.    From Wordnet, Princeton University. 

Adjective : a liveried footman.    From Dictionary.com. 

The car is unliveried but everyone out on the street knows perfectly well it's the police.    From Wordnik.com.  [Manchester Evening News - RSS Feed] Reference

As for you, unblushing parasite, uncrowned king of unliveried servants, leave your real character at home, let your digestion keep pace with your host's laugh when he laughs, mingle your tears with his, and find his epigrams amusing; if you want to relieve your mind about him, wait till he is ruined.    From Wordnik.com.  [The Magic Skin] Reference

Aboo-Obeidah of his eulogy, and suffered himself, without an attendant, to be ferried across to Roumeli-Hissar; when he there took an humble wherry of two oars, and bade the unliveried Greeks who served them pull for Therapia, it was to see again the woman who was taking his fancy into possession, not Constantine and his court bizarre in splendor and habitude.    From Wordnik.com.  [The Prince of India — Volume 01] Reference

On reaching the apartment of the astrologer the four disguised courtiers remained respectfully upon the threshold, while their unliveried representatives advanced to the middle of the room; and courteously saluting their host, informed him that they had been induced by his great renown to solicit a display of his skill, and to claim from him a knowledge of their future fortunes.    From Wordnik.com.  [The Life of Marie de Medicis — Volume 2] Reference

As for you, unblushing parasite, uncrowned king of unliveried servants, leave your real character at home, let your digestion keep pace with your host’s laugh when he laughs, mingle your tears with his, and find his epigrams amusing; if you want to relieve your mind about him, wait till he is ruined.    From Wordnik.com.  [The Magic Skin] Reference

All was light, order, and comfort; but nothing that indicated that the sudden arrival of so many unexpected guests had occasioned either hurry, or had brought forth any appearance beyond that of the ordinary mode of living; she could scarcely, however, repress a smile when she saw an unliveried attendant at the side board, who made no part of her household, but whom she immediately recognized as a nephew of Mr. Roberts, who in the life-time of Mr. Willoughby’s father had filled the station, which it seemed, from the propriety and habitual ease with which he now performed the office, he could never have quitted.    From Wordnik.com.  [Isabella. A Novel] Reference