You can get latest officially released version from this site gtktetcolor-0.6.4.tar.gz, gtktetcolor-0.6.4.tar.bz2 or from ibiblio.org (if available).
Windows XP executable file (built against gtk+-2.4 from http://www.gimp.org/~tml/gimp/win32/ ) gtktetcolor-0.6.4-win.zip. Download Gtk+ installer from http://gimp-win.sourceforge.net/ (gtk+-VERSION-setup.zip) in order to run this executable file.
Older versions: