I guess I never thought about their vision, but my favorite cephalopod is the octopus. A skilled hunter, and a master of disguise. As a diver I have seen them change color and texture to camouflage themselves. I would be surprised if they couldn't see color, they manage to mimic it so well.
I prefer the warm waters of the Caribbean, and on a night dive I always take the opportunity to turn off the light and wave my hand rapidly back and forth to stimulate the bioluminescence.