Color Posts grabs an image from your post, samples it, creates a matching color and a contrast value (black or white), and changes the post’s background color to match the image. It also changes the background color of your window in Chrome for Android, and customizes the look of the AMP default template if you use the AMP plugin.
If you’re not happy with the automatically picked color, you can define your own custom color thanks to the “Post Color” meta box in the post editor.
If you’d like to use post colors via the REST API, you can use the colors field in the post response.
Important: for this plugin to work, you must activate Jetpack first.
If you find bugs, you can report them here, or submit a pull request on GitHub.
You can read more about how the plugin works here: Color Posts plugin: how to use Jetpack libs in your plugin