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