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