Port and starboard for the sailors are
signals as for others left and right.
But red and green for drivers of a car
draw their attention only by their light.
The choice of red and green, however,
points to their contrast which says either or,
mistaking left for right is never clever,
not stopping at a red light you deplore.
Nature, you see, puts red and green together
and other colours, which you wouldn’t dare.
It never once must wonder whether
sailors or drivers are supposed to care.