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