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