Poohb if you check out PJSM site you can view the two covers with the same title one is a hardcover of the two originals graphic novel and the other is the 25th Anniversary edition. But I have not any other details on it yet.
Comics: Colour of Magic: illustrated by Steven Ross and adapted by Scott Rockwell (1992)
The Light Fantastic: illustrated by Steven Ross and Joe Bennet (1993)
Mort: drawn by Graham Higgins (1994)
Guards Guards: drawn by Graham Higgins and based on Briggs' script (2000)
Illustrated Novels: Eric: illustrated by Josh Kirby (1990)
The Last Hero: illustrated by Paul Kidby (2001)
That was 10 minutes work on Wikipedia and Amazon.co.uk.
I am one f those jammie people that have all the graphic novels incloding Eric, plus al the rest you ave allready said, i got them by chance from book shops and off Amazon and I did not pay that much for the, they are in good condition too. The colour of magic graphic noval was the one that got e stated on reading discworld and after that like u all I was huced line and sinker lol