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)(16,21)(17,22)(18,24)(20,23)(25,26)(27,30)(28,31)(29,32)(33,37)(34,38)(35,39)(36,40) involution — undirected(1,3,6,7)(2,4,5,8)(10,14)(11,17)(16,19)(18,20)(25,26,29,32)(27,30,33,37)(28,31,36,40)(34,38,35,39)(1,4,6,8)(2,7,5,3)(10,14)(11,17)(16,19)(18,20)(27,33)(30,37)(34,35)(38,39)(1,2,6,5)(3,8,7,4)(9,10)(11,15)(12,16)(13,14)(17,22)(18,23)(19,21)(20,24)(25,26)(27,30)(28,31)(29,32)(33,37)(34,38)(35,39)(36,40)(1,4)(2,3)(5,7)(6,8)(9,11,13,17)(10,15,14,22)(12,20,21,18)(16,24,19,23)(25,27,29,33)(26,30,32,37)(28,35,36,34)(31,39,40,38)(1,5,6,2)(3,8,7,4)(9,12)(10,16)(11,18)(13,21)(14,19)(15,23)(17,20)(22,24)(25,28,29,36)(26,31,32,40)(27,34,33,35)(30,38,37,39)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.