You can discover what the default visual is for your X-server by running the program xdpyinfo and looking for the default visual id, then looking for the description of that visual. You can tell xv to use a visual other than the default by giving it the -visual flag when invoked, or setting the X resource xv*visual. I set this resource to the string TrueColor, which seems to solve the trick.
Another problem that some people have is that their gamma correction is not in concert with the rest of the world. If somebody tells you to run some sort of experiment where you put a checkerboard on your screen and stand far away from it -- don't listen to them. They are well-intentioned, but confused. If they tell you that the gamma of your monitor is something different than 2.2, send them to me and I'll explain to them why they are totally insane.
The pictures on my page have already been gamma-corrected, by
the way. (Ok, well, most of them....)
