N.Y. Mult. Resid. Law § 56
Every means of egress shall be indicated by a sign reading "EXIT" in red letters at least eight inches high on a white background, or vice versa, illuminated at all times during the day and night by a red light of at least twenty-five watts or equivalent illumination. Such light shall be maintained in a keyless socket. On all stories where doors, openings or passageways giving access to any means of egress are not visible from all portions of such stories, directional signs shall be maintained in conspicuous locations, indicating in red on a white background, or vice versa, the direction of travel to the nearest means of egress. At least one sign shall be visible from the doorway of each room or suite of rooms. Existing signs and illumination may be accepted if, in the opinion of the department, such existing signs and illumination serve the intent and purpose of this section. Supplementary stairs, fire-stairs or fire-escapes which do not lead to the entrance story or to a street or to a yard or court, leading to a street, shall be clearly marked "NOT AN EXIT" in black letters at least four inches high on a yellow background, and at the termination of each such stair, fire-stair or fire-escape, there shall be a directional sign indicating the nearest means of egress leading to a street. All signs shall be constructed, located and illuminated in a manner satisfactory to the department.
N.Y. Mult. Resid. Law § 56