Current Experimental Operating Limitations (NOTE: you'll need to look at your particular airplane's Op Lims, as they have gone through several iterations over the past 20 years...), per FAA Order 8130.2F, Part 153, states:
" 8 After completion of phase I flight testing, unless appropriately equipped for night and/or instrument flight in accordance with §91.205, this aircraft is to be operated under VFR, day only."
What this means is that for you to operate an Experimental aircraft at night, even though §91.205 is titled, "Powered civil aircraft with standard category U.S. airworthiness certificates: Instrument and equipment requirements", you still need to comply with the lighting requirements under this regulation.
The particulars of equipment necessary for Night VFR operations, per §91.205(c), are thusly:
c) Visual flight rules (night). For VFR flight at night, the following instruments and equipment are required:
(1) Instruments and equipment specified in paragraph (b) of this section.
(2) Approved position lights.
(3) An approved aviation red or aviation white anticollision light system on all U.S.-registered civil aircraft. Anticollision light systems initially installed after August 11, 1971, on aircraft for which a type certificate was issued or applied for before August 11, 1971, must at least meet the anticollision light standards of part 23, 25, 27, or 29 of this chapter, as applicable, that were in effect on August 10, 1971, except that the color may be either aviation red or aviation white. In the event of failure of any light of the anticollision light system, operations with the aircraft may be continued to a stop where repairs or replacement can be made.
(4) If the aircraft is operated for hire, one electric landing light.
(5) An adequate source of electrical energy for all installed electrical and radio equipment.
(6) One spare set of fuses, or three spare fuses of each kind required, that are accessible to the pilot in flight.
So, before you install a set of lights from Chet's Hotrod Shop on your flying Whatchamadigit, you'd better make sure you comply with §91.205(c), which is likely to entail that position and anticollision lights meet the lighting requirements given 14CFR Part 23 (for the size airplanes we fly).
My two bits,