Dreaming in color - I don't even see where you're going with this. Some people do, some don't. It changes over time. Where's the error? Are there people who think they dream in color but don't, or vice versa? How is this relevant?

It surely seems improbable that most of people in the 1920s were dreaming black and white while today 80% dream in color. The perceptions can be culturally influenced in principle (I don't assume a significant biological change happening during the 20th century), but it is far more probable that a substantial part of people report about their subjective experiences incorrectly. The probable reason is that people can't remember what their dream was exactly like (or perhaps it even has no sense to speak about colors in dreams) and their report is contaminated by their expectations of what it should be, which are more easily subject to cultural influences. We may say that the flaw is in the memory and not in the experience itself, but that doesn't contradict the point of the original post. Lukeprog hasn't said that the experiences are wrong, but only that people can be wrong even about thier own experiences - and inconsistent reporting about the quality of dreams certainly requires being wrong about them.