How can I optimize VNC
 

How can you get vnc to perform better with a slow connection. As in dial up.

Thanks in advance.

reduce color depth and/or resolution

I've been managing dozens of computers via RealVNC over a slow dialup (28.8) for a while now.
In RealVNC the client can lower color depth to as low as 16 colors - no need to change anything on the server side. If using the realvnc server (i think this is the one that comes with most redhat/fedora releases?) you can also have it automatically remove any background image and restore once the client disconnects - this speeds things up slightly too - but running in 16 colors is definitely the way to go if you want real speed and looks don't matter.

How do I do this ? Is it possible to change the colour depth on the server side and if so how.

my apologies - looks like only the windows server can remove the background automatically - but still, if you set the background to a solid color in general it will speed up the vnc performance

and you dont need to chang ecolor depth on the server-side - you change it in the client and the information is passed on to the server which automatically just sends the client more/less data based on what color depth youve chosen. you change the color depth in the options menu (right-clicking the title bar) on windows, or as flags on the binary in linux