I don’t know why, but I’ve found Importance of Achromatic Contrast in Short-Range Fruit Foraging of Primates strangely fascinating. Here’s a snip:

Despite these findings, behavioral observation of wild primate populations has given a limited support for trichromat advantage. In a study of wild mixed-species troops of saddleback (Saguinus fuscicollis) and mustached (S. mystax) tamarins, trichromats are further from their neighbors than their dichromatic conspecifics are during vigilance, which is explained through the potentially better perception of predation risk in trichromats [33]. Results of many other field observations are equivocal or opposite to the pattern expected of the trichromat advantage hypothesis.

One reason is the simplicity (but amazing complexity and importance) of the question: so what’s the advantage then of trichromacy?

By simplicity I mean: the basic questions matter still and still need pursuing. It’s a fascinating piece.

Thanks to Bora Zivkovic for the original link.