User-submitted colour palettes accessible through an API.

User-generated tagged colour palettes. With a nice API.

Comma-Separated Value dataset of 10,000 colours and the labels applied to them by Amazon Mechanical Turk clickworkers. Archive contains the dataset and useful accompanying...

Colours and palettes submitted by users, accessible through an API.

An article showing colour palettes taken from famous paintings, with more in the comments. This isn't really a package, but it's a good resource and a great illustration of...