iMore reports: [edited]
Skala, Bjango's next generation interface design tool for Mac, is still under development but a component of it, Skala Color, has just launched — and it's free for everyone.
Skala Color is a compact and feature-rich OS X color picker that works with a huge variety of formats, covering everything you're likely to need for web, iOS, Android and OS X development — Hex, CSS RGBA, CSS HSLA, UIColor, NSColor and more. It also automatically recognises colours copied to the clipboard, presenting them as a swatch that can be applied with a single click.
Video explanation below: