If your browser supports CSS properly, then you might find this html color picker useful.
I got really tired of not being able to find a list of colors that included more than a few hundred colors, or a GUI color picker thing for Linux or some other unixy thing, so there I went ...
color pickers (shamelss self-plug)
wickline on 2002-07-17T10:41:46
here's one that
1) also has too few colors
2) requires frames
3) requires decent ecmascript support
4) probably has other associated lamenesses
but on the plus side
1) lets you select sets of colors (web site color scheme)
2) shows how colors work as text on background
3) lets you see how they might look to color blind visitors
4) attempts to simulate gamma differences as well
http://colorlab.wickline.org/
-matt
