One vertex per element, one color per generator, with an edge from x to x·s.
(1,2,5,7,6,3,4,8)(9,10,14,20,15,19,13,18)(11,21,24,31,25,16,23,32)(12,26,27,34,28,17,29,33)(22,30,36,39,37,35,38,40)(1,3)(2,6)(4,8)(5,7)(9,11,15,25)(10,16,19,21)(12,22,28,37)(13,24,14,23)(17,30,26,35)(18,32,20,31)(27,38,29,36)(33,40,34,39)(9,12,15,28)(10,17,19,26)(11,22,25,37)(13,27,14,29)(16,30,21,35)(18,33,20,34)(23,36,24,38)(31,39,32,40)(1,4,6,5)(2,7,3,8)(9,13,15,14)(10,18,19,20)(11,23,25,24)(12,27,28,29)(16,31,21,32)(17,33,26,34)(22,36,37,38)(30,39,35,40)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.