>Does anyone have a list of the 256 RGB combinations that appear non-dithered? Or how do I calculate them?

I think the true non-dithered are RGB combinations of 0, 128, and 255, plus a 192 for gray...you can see the basic 16 by opening the vfp Color Palette (the one with 16) and taking a label and altering it with the PEM sheet open. All these colors are "safe" for old 16-bit usage...