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