Rainbowpicker is a Firefox addon, a copy of the advanced colorpicker that can be found in Nvu and ported over to Firefox (and it should also work with Flock). It also adds a toolbar button and a Tools menu option to bring it up to copy a color to the clipboard. All it does is replace any button colorpicker elements with a different binding which displays the colorpicker dialog instead of the small 70-color pop-up.

The license of this software is Freeware, you can free download and free use this browser plug-ins software.