Hi Phoebe,
It's odd that you get that "TrueColor visual" error from suma,
but have no similar problem with afni. You might be able to
set TrueColor in some Display configuration...
In any case, there appear to be 2 problems. One is that you
don't have accelerated drivers installed. The other is that suma
should work even without them, though slowly (software rendering,
instead of hardware rendering), except that you are getting the
TrueColor error.
Properly installing video drivers would probably correct both
problems, but it can be non-trivial, depending.
Do you know anything about this? If not, do you have a system
administrator who does?
What video card are you using?