Eye color and shape are helpful in identifying some species, but not all.
The only Gonodactylus that I can always tell just by eye color is G. platysoma. The whitish green eyes are unique.
Other examples of easily identified species by eye color are Chorisquilla tweediei with black and whit stripes, Lysiosquillina maculata with spots, and Pseudosquilla ciliata with a checkerboard pattern.
N. wennerae eyes vary to some degree with respect to color and some are a reddish maroon.
Roy