son1 has written a post that continues the discussion I began around colors and data visualization, and I’m jealous of it for two reasons. First, I can’t believe I didn’t think of and claim that post title for myself, because it’s perfect.
Second, he does a much better job of getting to the heart of what I was trying to express: that a surprisingly large amount of data visualizations are both correct and question-begging. The choices made by the creator will inevitably influence which conclusions are drawn. That isn’t to malign the idea of graphs and charts and maps — at their best they are arguments that contain all component data, and whose accuracy can be easily checked. But they’re still arguments.
Perhaps all this stuff has been said before and better by Tufte, but those books are expensive, dammit.
I’ve got all three Tufte books on my shelf here, and I don’t recall any mention of this particular issue when it comes to color…
… quickly leafing through Visual Display of Quantitative Information. Ah! Here we go. Pages 153 and 154, we get a map with a multidimensional color scale.
So he seems to mention color in that one spot, and not much else (at least in that book; it’s been a while since I scanned his others…). My impression is that he mostly focuses on the geometrical aspects of his charts, and the relationship of that geometry to the underlying numerical values, and that his main recommendation for color is Not to Use It.
I think that most of the criticism that you and I have been making, though, would still apply to grayscale too. Linear interpolation between black and white might be better, but not much better.