I just stumbled on to Remmina and have found it to be a breath of fresh (RDP) air.
For the RDP color options it offers are; 256, 16 bit, 24 bit and (my favorite because it looks as good 16 bit, at fraction of the bandwidth) 15 bit.
For better performance on slow connections; I use 15 bit color (256 is painful), disable everything except local caching (the Quality setting set to Poor in Remmina) and will also set the resolution (window size) smaller if the connection is still slow.
If you are using Unity, you may want to create a custom resolution for your particular monitor, to simulate a full screen mode.
Remmina is a remote desktop client written in GTK+, aiming to be
useful for system administrators and travellers, who need to work with
lots of remote computers in front of either large monitors or tiny
netbooks. Remmina supports multiple network protocols in an integrated
and consistant user interface. Currently RDP, VNC, NX, XDMCP and SSH
are supported. Remmina is released in separated source packages:
"remmina", the main GTK+ application "remmina-plugins", a set of
plugins Remmina is free and open-source software, released under GNU