which American comic-book limited series published by DC Comics was John Higgins a colourist for
John Higgins (comics):  He did significant work for "2000 AD", and he has frequently worked with writer Alan Moore, most notably as colourist for "Watchmen". Watchmen: Watchmen is an American comic-book limited series published by DC Comics in 1986 and 1987, and collected in 1987.
Watchmen