The conventional solution

It is normally possible to run these programs without additional effort on Sun and DEC machines because they supply a PseudoColor visual whatever the mode of the X display. To run them on a Linux PC however, it is usual to set the X display to run in 8-bit mode, by starting it with a command like

xinit -- -bpp 8

The programs then work fine, but the colour map can easily fill up causing programs to fail or images to look poor, and the big powerful video card (if such is installed) is being used at a fraction of its capabilities.