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