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