The Monochromatic Octopus: A Unique Eye Shape

All throughout the animal kingdom we have monochromats, dichromats, trichromats and tetrachromats. An octopus has only one kind of photoreceptive cell to generally like a rod. It could be that with only rods, they are still able to have a brain's response to color because they are actually seeing wavelengths hitting at different sort of angles on the eye based on its shape.