Today I Learned
Cubehelix, not Rainbow
Here in a series of posts by MYCARTA, the author Matteo analyzed the drawbacks of rainbow. Problems such as non-monotonic changing of brightness can cause serious problems for figures and plots.
Cubehelix comes to the rescue. Other alternatives can also be very helpful, such as viridis.
D3.js
D3.js has a cubehelix plugin that contains the cubehelix color palette.
Python
Many python modules has implemented cubehelix. Such as jradavenport/cubehelix.
Mathematica
Here is the cubehelix code from JasonB@stackexchange. He also made it avaible online through <<"http://pastebin.com/raw.php?i=sqYFdrkY";
Download the Mathematica notebook here.