1. http://www.hsluv.org/examples/ These palettes will absolutely NEVER clash. But they might have contrast issues. Which brings us to:
2. https://news.ycombinator.com/item?id=19800718 Lyft primarily designed ColorBox.io to always reach WCAG 2.0 contrast ratios. Something I'd claim a ton of UX themes mess up. Unfortunately from what I can tell, it lacks the anti-clash guarantees of #1
3. Much less related, but still important, albeit only for very specific parts of any UX:
The color map generation approach in Matplotlib: https://www.youtube.com/watch?v=xAoljeRJ3lU (btw.: Seaborn, as mentioned in #1, builds on top of Matplotlib.)
For even more color madness, see this recent Hacker News comment by me as well as the other comments linked to there: