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