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)(13,19)(14,18)(15,28)(16,22)(17,25)(21,36)(23,32)(26,34)(27,31)(29,33)(30,38)(35,39)(37,40)(1,3,4,2)(6,7)(9,11)(10,16)(12,21)(13,27)(14,22)(15,23)(17,30)(18,20)(19,32)(24,40)(25,39)(26,37)(28,31)(29,38)(33,35)(34,36)(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)(10,18)(11,22)(17,33)(19,28)(21,37)(23,27)(24,34)(38,39)(9,13,14,15)(10,19,18,28)(11,23,22,27)(12,25,26,29)(16,31,20,32)(17,34,33,24)(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.