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