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