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