Cool! I knew there had been some useful tools posted on the earlier thread but didn't have time to dig them out. Interesting observation about the colorfulness. I don't know enough about all the transformations involved to full account for that, but I added some stuff to the notebook to figure out how much of that might be caused by straying out of gamut. It looks like the map I created does a pretty good job and is only getting clamped at the very low end and near the high end, so I don't think it's a complete explanation for the undulating "colorfulness": http://nbviewer.ipython.org/gist/mwaskom/6a43a3b94eca4a9e2e8b By means of disclosure, I did this before having coffee, so it might be wrong...