According to your PA DMV site:
175.80. Inspection procedure.
(9) Check the lamps and lenses and reject if one or more of the following apply:
(i) An exterior bulb or sealed beam, if originally equipped or installed, fails to light properly, except ornamental lights.
(ii) The turn signal lamps do not flash between 60-120 flashes per minute.
(iii) The turn signal lamps do not properly indicate right or left or hold in position when so switched or do not self-cancel if originally designed to do so.
(iv) The back-up lamps do not turn off automatically when the vehicle goes forward, there is no indicator on dash that lights or there is no audible warning signal.
(v) The lamp shows a color contrary to the lighting chart.
(vi) The lamp or filament indicated at the switch position does not light when the correct switch indicates the lamp should be on.
(vii) The lamp has a missing or broken lens.
(viii) A required lamp is missing.
(ix) The auxiliary equipment is placed on, in or in front of a lamp.
(x) The fog lamps operate with the high beams of the headlamps or are substituted for the low beams.
(xi) The auxiliary driving lamps operate with the low beam of standard headlamp system or alone.
(xii) The headlamps are out of adjustment as follows:
(A) Mechanical aimer:
(I) The horizontal aim is more than 4 inches to the left or right.
(II) The vertical aim is higher or lower than 4 inches from center.
(B) Screen or photo electric type tester. See Charts 1-3 (relating to headlight aiming screen distance and marking identification; high beam inspection limits; and low beam inspection limits).
(I) Turn the lamps on high beam and reject if the center of the beam is horizontally more than 4 inches to the right or left of ''straight ahead'' or if center of light beam is vertically more than 4 inches above or below horizontal line.
(II) Turn the lamps on low beam and reject if the upper edge of the beam is more than 4 inches above or below horizontal center line of headlamp or if inner edge of beam is more than 4 inches to the right or left of the vertical line.
175.125. Lighting and electrical systems.
(a) Condition of lamps and switches. Every required lamp or switch shall be in safe operating condition as described in § 175.130 (relating to inspection procedure).
(b) Lighting standards. Lamps shall comply with Tables II-IV; Chapter 153; and 75 Pa.C.S. Chapter 43 (relating to lighting equipment).
(c) Other required lamps. A trailer shall have at least one red stop lamp on each side of the rear of the vehicle, which shall be illuminated immediately upon application of the service brake.
(d) Illumination. A trailer shall be equipped with parking lamps, stop lamps, tail lamps, turn signal lamps and hazard warning lamps designed for that specific function, which under normal atmospheric conditions, shall be capable of being seen and distinguished during nighttime operation, at a distance of 500 feet. See 75 Pa.C.S. § 4303(b)-(d) (relating to general lighting requirements).
(1) Stop lamps, turn signals and hazard warning lamps shall be visible at a distance of 100 feet during normal sunlight.
(2) Rear lamps shall be lighted whenever headlamps, fog lamps or auxiliary driving lamps are in operation.
(3) A trailer shall be equipped with hazard warning lamps, unless these lamps were not included as original equipment.
(4) The turn signals shall have a frequency of flash between 60-120 flashes per minute.
(e) Condition and position of lamps. Lamps shall be properly fastened; direct light properly; be of a color not contrary to regulations-see Tables II-IV (relating to required motor vehicle lighting equipment; location of required equipment; and required motor vehicle lighting equipment); and may not be so obstructed by a screen, bar, auxiliary equipment or device of any kind as to obscure, change color of or obstruct the beam.
(f) Ornamental lamps. A lamp not enumerated in this section, and not located as described in Tables III-V of this chapter is prohibited unless it is available as original equipment. An illuminated sign is prohibited. Flashing or revolving lights are not ornamental lamps. Provisions relating to flashing or revolving lights are located in Chapters 15 and 173 (relating to authorized vehicles and special operating privileges; and flashing or revolving lights on emergency and authorized vehicles).
(g) Back-up lamps. Back-up lamps, if the vehicle is so equipped, shall turn off automatically when the vehicle goes forward.
(h) Registration plate lamp. A registration plate lamp, if originally equipped, shall emit white light and make the registration plate visible from a distance of 50 feet to rear of the vehicle.
(i) Exception. A trailer that is less than 30 inches in overall width may be equipped with only one of each of the following lamps and reflective devices, located at or near its vertical centerline: tail lamps, stop lamp and rear reflex reflector.
The provisions of this § 175.125 amended under the Vehicle Code, 75 Pa.C.S. § § 4103, 4301, 4501, 4521 and 6103.
The provisions of this § 175.125 adopted October 29, 1982, effective February 1, 1983, 12 Pa.B. 3862; corrected November 12, 1982, effective February 1, 1983, 12 Pa.B. 3947; readopted December 2, 1988, effective December 3, 1988, 18 Pa.B. 5362; amended November 13, 1998, effective May 13, 1999, 28 Pa.B. 5670. Immediately preceding text appears at serial pages (221279) to (221280).
If I were you, I´d send an e-mail to someone here
and ask them for anything specific, or to send you copies of the aforementioned legal chapters. I´ve recieved prompt replies from the NC DMV concerning lighting. Good luck.