Color libraries

• color
• color.js - Color management utilities, MIT
• color-js
• colour.js
• colorjs
• RGBColor - RGB color parser (converts CSS color names to something useful)
• color2color
• repl-rainbow - Convert between RGB-HSL-Ansi256, creates functions to auto escape terminal text. Targeted at trivializing incredible rainbows in the console.
• jQuery xColor - plugin for jQuery
• one-color
• jcolour
• rainbow-dash - Very fast color interpolation in Javascript
• chroma.js - color library which supports all the obvious color spaces plus CIElab and HCL (why you may want to use these, see https://vis4.net/blog/posts/avoid-equidistant-hsv-colors/ and http://en.wikipedia.org/wiki/Lab_color_space )

Other

• Color conversion math and formulas