How to prevent "colour level" from going up?

Seak, Teng-Fong lapsap7+vnc "at" gmail.com
Tue Mar 17 20:48:01 2009 

     I just don't understand: in my VNC file it's specified that I use "Low
(64 colours)" as "Colour Level" (because of low bandwidth).  But once the
whole screen is drawn, VNC (don't know if it's the client or the server)
just keeps on "upgrading" the "Colour Level"!!!

     Why I can't specify the colour level?