Les Colregs précisent :

7. Color specification of lights
(a) The chromaticity of all navigation lights shall conform to the following
standards, which lie within the boundaries of the area of the diagram
specified for each color by the International Commission on Illumination
(CIE).
The boundaries of the area for each color are given by indicating the
corner coordinates, which are as follows :
(i) White :
x 0.525 0.525 0.452 0.310 0.310 0.443
y 0.382 0.440 0.440 0.348 0.283 0.382
(ii) Green :
x 0.028 0.009 0.300 0.203
y 0.385 0.723 0.511 0.356
(iii) Red :
x 0.680 0.660 0.735 0.721
y 0.320 0.320 0.265 0.259
(iv) Yellow :
x 0.612 0.618 0.575 0.575
y 0.382 0.382 0.425 0.406

Soit sur le graphe CEI, les zones indiquées. On remarque que la définition du vert est limite bleue...