Iris is the color picker that ships with the newest WordPress release, v3.5. It is also the color picker you'd see when customizing your WordPress.com blog, originally created to power their Custom Colors feature.
Without the regular whistle and bells that Automattic uses to promote its regular products, Iris was recently open sourced on GitHub, the company deciding that it was time to share it with the world and released it as a stand-alone package for developers everywhere.
The color picker uses lots of CSS 3 in its interface, so beware of cross-browser rendering issues, since it will show properly only in capable browsers.
As for the design and usability, Iris' UI kind of resembles Photoshop's color picker, with less options but the same use patterns. Overall, it looks extremely nice, handles without a glitch and loads pretty fast, even with multiple instances on the same page.
If you feel you have anything new to contribute to the project, development is handled via Automattic's GitHub account.
Download Iris from our Scripts section here.