yes that is true but with the pegasos as with other pcs you have only 8bit of vga ,where as the classic amiga has 24bit of r g b. Which is why you wouldnt show the colors so right.SO its not true png with pegasos .Use a Sgi made png and then use a pc to try and read it right, same thing as pegasos . It wont read or show the png right. To fuzzy. Sgi differnt more true colors per bits.

The Amiga is 24bits with and extra 8bit.

But still the card should show more then the true 2 bits per channel you are now showing. It is the driver.