Weaving the rainbow: Color-blind color matching in cephalopods

Cephalopod camouflage presents a longstanding paradox: many species appear to match the color of their surroundings, yet anatomical and behavioral evidence suggests they lack conventional color vision. Here I discuss behavioral, anatomical, optical, molecular, and ecological evidence bearing on this problem. I evaluate a range of proposed mechanisms that could reconcile color matching with monochromatic vision, including passive skin reflectance, chromatic aberration-based spectral inference, polarization vision, and extraocular photoreception. Each is found to be either insufficient or weakly supported by current data. I then consider the null hypothesis that cephalopods achieve effective color matching without color perception, drawing an analogy with machine vision systems that infer color from grayscale statistics. Cephalopod camouflage may rely on predictive mappings from luminance-based visual input to colored skin output, rather than on true color vision.