Most of the time you will need a color picker library that you can use inline or preferably as a pop that you can bind to a text box, multiple color palette selection, user friendly, works with any web frameworks, and cross-browser support.
A web color picker which looks like the one in Microsoft Office 2010. It can be used inline or as a popup bound to a text box. It comes with several color palettes, can track selection history and supports transparent color.
An easy-to-use jQuery color picker for Twitter Bootstrap, designed to be easy for anyone to use, based on Twitter Bootstrap styles so it looks lovely with the styles of almost any site.
Colorjoe is a truly scaleable color picker, based on CSS and does not depend on external images, you can tweak its size to fit your purposes. Supports touch and AMD module definition as well.
FlexiColorPicker is based on HSV color model. The only two parts of the color picker are therefore the slider for selecting hue value and the picker for selecting saturation and value.