gitk python script will read rgb value from rgb.txt
Solution
1. Get rgb.txt from http://ftp.sunet.se/pub/www/utilities/www-tools_uni-karlsruhe/rgb.txt
2. Save to /usr/share/X11 folder
3. Create a link under /etc/X11
4. Restart vncserver
if somecolor is still missing, even cannot find in rgb.txt, please add it into the rgb.txt.
e.g.
128 128 128 darkgrey
