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