WISH Color Picker Plus megawidget
http://www.geocities.com/pa_mcclamrock/
WISH Color Picker Plus is a fairly versatile megawidget for applying user-selected color schemes to Tk applications. After downloading and unwrapping the "wishcolorplus.tcl.tar.gz" archive, just put some code like this in your application:
(Revised code for 2008 version forthcoming soon--but not this morning--sorry!)