The “angry rainbow” palette is the colors you get when you set saturation and value to 100% and then spin the hue wheel. From bright red #ff0000, briefly through yellow, a long linger in #00ff00 green, longer still around dark blue #0000ff, and finally back to red via an eye-searing trip through purple. The term “angry rainbow” isn’t in common usage but I’m doing my best to spread it. I got the term from someone else, maybe another student at the MIT Media Lab? (See also: angry fruit salad).

The angry rainbow is always the wrong palette for data visualization. It’s too bright, too colorful, and too reliant on non-uniform hue discrimination. But it pops up all the time, from random weather maps to heatmap examples to NYTimes work sketches. It seems to be the default palette for various visualization tools, no doubt because it’s easy to generate in software. I’ve certainly been guilty of using it myself, somehow it’s always at my fingertips.

So what’s a better choice? Honestly, almost anything. Even knocking saturation and value down to about 80% gives a more pleasing result. If you have continuous data try plotting it with varying brightness instead of hue, or narrowing down to a red/blue color ramp (properly interpolated) instead of the full rainbow. if you want to do it right consider a ColorBrewer scale; the D3js implementation is a fine place to start. If you roll your own palette, work with colors that are not fully saturated and not fully bright. Think carefully about whether hue is really the thing you want to vary.