Text in force at 25-153: from 25-27, effective 11 Aug 1971.
Each position light color must have the applicable International Commission on Illumination chromaticity coordinates as follows:
(a) Aviation red-- "y" is not greater than 0.335; and "z" is not greater than 0.002.
(b) Aviation green-- "x" is not greater than 0.440 - 0.320y; "x" is not greater than y - 0.170; and "y" is not less than 0.390 - 0.170x.
[(c) Aviation white-- "x" is not less than 0.300 and not greater than 0.540; "y" is not less than "x - 0.040" or "y0 - 0.010", whichever is the smaller; and "y" is not greater than "x + 0.020" nor "0.636 - 0.400x"; Where "y0" is the "y" coordinate of the Planckian radiator for the value of "x" considered.]
36 FR 12972 · Source