Web Colour Data is a web application for extracting color profiles from websites.

Web Colour Data actually delivers not only color palettes, but intelligently breaks down the colors used in the website requested.

The web app illustrates the hues with a nice distribution graph and even shows a color wheel that pinpoints the colors. Indispensable for designers.

Spectrum is a jQuery colorpicker that sports most of the features you’d ever need from a color picker.

It doesn’t require any images and is heavily customizable. You can use it as a regular script or opt for the polyfill option for HTML5.

You can put your own color palettes inside of Spectrum; the plugin also comes with alpha transparency and handles most of the color formats out there.

iWantHue is a web app for generating color palettes; it provides a number of useful settings that intertwine with each other.

You can use the app to generate palettes of distinct colors that don’t bite the eyes despite being a motley mix.

The app provides a number of useful formats, such as RGB, HEX and JSON, and presets for are provided as well for those who don’t want to spend much time generating a palette.

jQuery.BlackAndWhite is a plugin for converting colored pictures to greyscale. 

You can use the plugin inside image galleries to achieve a chic effect, as in the picture the highlighted images is in color so it stands out.

The plugin uses HTML5′s canvas tag, but includes a fallback for older browsers as well.

Web Safe Colors is a website listing hex and RGB codes for all the major colors of the web.

The idea behind this project is to provide an easy to use palette of colors that’s laced with nostalgia for 8-bit color screens.

The website also features some palette choices; e.g., you can opt to view only earth tones, reds/greens, blues/greens and so on.

one-color is a JS/Node library for color manipulation.

 Available for modern browsers, and <IE9 with polyfill, this library offers powerful color manipulation with a chainable API and numerous other features.

The library supports color names in its bloated version, as well as alpha channels and the aforementioned, all-powerful API.