[P]eople don’t know whether they dream in colour. Dreams may not even have associated colours one way or the other! Indeed, when I asked a few friends and family whether they dreamed in colour, a surprising number of them answered “I don’t know”.
I don’t know much about the science of dreams, but I suspect that the answer may be that many dreams activate rods but not cones (or, at least, activate the parts of the brain that receive signals from rods). When it’s dark, and my cones are not receiving enough light to function, I wouldn’t describe the world I see as “black and white”—it seems different than that—but I also can’t see color. Perhaps many people’s dreams work the same way. (I find that, in many of my dreams, the dream world is dark enough that I can’t see color.)
I don’t know much about the science of dreams, but I suspect that the answer may be that many dreams activate rods but not cones (or, at least, activate the parts of the brain that receive signals from rods). When it’s dark, and my cones are not receiving enough light to function, I wouldn’t describe the world I see as “black and white”—it seems different than that—but I also can’t see color. Perhaps many people’s dreams work the same way. (I find that, in many of my dreams, the dream world is dark enough that I can’t see color.)