colorjoe - The Scaleable Color Picker
colorjoe was somewhat inspired by ColorJack and RightJS Colorpicker. Unlike those it actually scales pretty well. Essentially this means that you'll be able to define its actual dimensions and layout using a bit of CSS. This way the widget fits well responsive layouts.
In addition it's relatively easy to implement missing functionality (RGB fields, whatnot) thanks to the simple API it provides.
colorjoe is available under MIT. See LICENSE for more details.