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