[Buetol]

Looks like the link to the "I want HUE" tool is broken, here's the proper link: http://medialab.github.io/iwanthue/

[azepoi]

I'm impressed by the other mentioned picker, for HCL this time http://tristen.ca/hcl-picker/

This tool is also useful https://vis4.net/palettes/#/9|s|00429d,96ffea,ffffe0|ffffe0,...

I have to mention this fantastic presentation on colormaps https://www.youtube.com/watch?v=xAoljeRJ3lU (A Better Default Colormap for Matplotlib, SciPy 2015, Nathaniel Smith and Stéfan van der Walt). It is about perceptually uniform colormaps. https://bids.github.io/colormap/