ColorZilla

ColorZilla is a Mozilla extension that assists web developers and graphic designers with color related and other tasks.

ColorZilla allows getting a color reading from any point in the browser, quickly adjusting this color and pasting it into another program, such as Photoshop.

The extension allows zooming Web pages and measuring distances between any two points on the page. The built-in palette browser allows choosing colors from pre-defined color sets and saving the most used colors in custom palettes. DOM spying features allow getting various information about DOM elements.