Currently a pretty basic/ugly color picker is present in for example in popup_gitem.php. It would be nice if it could be replaced by something like JSColor: http://jscolor.com/ , a very nice LGPL color picker ( more examples here http://jscolor.com/try.php ) that would be a drop-in replacement of the current one..

Secondly, the option to have "favorite colors" would be very nice as well, per user for example? Currently the default colors are pretty awkward