One vertex per element, one color per generator, with an edge from x to x·s.
(1,2,3,7,4,6,8,5)(9,10)(11,20)(12,26,30,37)(13,24)(14,18)(15,23)(16,19)(17,29,34,31)(21,25)(22,28,38,40)(27,36,39,35)(32,33)(2,5)(3,8)(6,7)(9,11,21,10,15,24,13,18,16,25,20,19,14,33,32,23)(12,27,35,37,31,38,40,17,30,39,36,26,29,22,28,34)(2,6)(5,7)(9,12,16,30)(10,17)(11,22)(13,28,32,40)(14,29,15,31)(18,26)(19,34)(20,35,21,36)(23,37)(24,27)(25,38)(33,39)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.