This is a collection of useful resources and tools to properly choose and generate colors for data visualizations. The order is more or less random.
Color Theory: Brief Guide For Designers by Alina Arhipova. An intro to color theory.
Choosing Colormaps in Matplotlib by Matplotlib. An overview of the matplotlib colormaps.
How to pick more beautiful colors for your data visualizations by Lisa Charlotte Rost.
This article describes how to properly choose adequate colors for visualizations. The article includes many visually appealing examples.
What to consider when choosing colors for data visualization by Datawrapper.
Another resource from Datawrapper with a focus on choropleth maps.
Beautiful colormaps for oceanography by Kristen Thyng. An overview of domain specifc colormaps.
https://coolors.co/ An overview of beautiful color palettes.
https://gist.github.com/camminady/bf4cd22488cc3af1afc09ff9f0db2db4 by myself. Generates somewhat distinct random colors.