When we were developing COPASO, we found that we needed to have a more advanced color picker to work inside the application and since COPASO is built with DHTML it was easy enough to pull out the picker to use on the other creation pages of our site. 
Ever tried using a color picker on a high resolution monitor? It is impossible. That is why this color picker has a magnifier attached. Grab palettes of up to 16 colors at once and use four advanced color mixers to select a spectrum of possibilities.
This colorpicker is based heavily upon the code from ColorMatch 5k. I have made it more compatible – it now works in Mozilla, and should also work in Opera, since I am using a much better slider control. 