14 CFR 29.1397 - Color specifications.
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 yc−0.010, whichever is the smaller; and
y is not greater than x 0.020 nor 0.636−0.400x;
Where Ye is the y coordinate of the Planckian radiator for the value of x considered.