Text in force at CS25-28: from CS25-0, effective 17 Oct 2003.
(a) General. Each part of each position light system must meet the applicable requirements of this paragraph and each system as a whole must meet the requirements of CS 25.1387 to 25.1397.
(b) Forward position lights. Forward position lights must consist of a red and a green light spaced laterally as far apart as practicable and installed forward on the aeroplane so that, with the aeroplane in the normal flying position, the red light is on the left side, and the green light is on the right side. Each light must be approved.
(c) Rear position light. The rear position light must be a white light mounted as far aft as practicable on the tail or on each wing tip, and must be approved.
(d) Light covers and colour filters. Each light cover or colour filter must be at least flame resistant and may not change colour or shape or lose any appreciable light transmission during normal use.
ED Decision 2003/002/RM · Source