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