I totally agree. Hard not to think about Edward Tufte when this comes up: "In color maps, use a single hue, Don't use up the entire color spectrum, or even all of a hue's levels. Particularly avoid Roy G. Biv (red, orange, yellow, green, blue, indigo, violet), the color spectrum of the rainbow. It's good physics, but poor human factors. Like all multi-hue color maps, the non-equidistant hue changes are perceived as especially important contours, which they usually are not. Furthermore, the lighter middle parts of the spectrum are often perceived as the higher values. Finally, one needs to constantly remind oneself which color means high vs. low values. Using a single hue with variations in intensity allows instant interpretation, multiple color maps without ambiguity, and leaves graphical space for layering and separation."