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)(11,16)(12,14)(13,17)(15,19)(18,24)(20,22)(21,23)(25,26)(27,33)(28,34)(29,37)(30,31)(32,38)(35,36)(39,40)(3,7)(5,8)(9,11)(10,15)(12,16)(13,18)(14,19)(17,23)(20,24)(21,22)(26,31)(27,34)(32,37)(35,40) involution — undirected(1,2)(3,5)(4,6)(7,8)(25,27)(26,28)(29,35)(30,34)(31,33)(32,36)(37,39)(38,40) involution — undirected(9,12,14,10)(11,16,19,15)(13,17,22,20)(18,23,21,24)(25,28)(26,27)(29,36)(30,33)(31,34)(32,35)(37,40)(38,39)(1,3)(2,5)(4,7)(6,8)(9,11)(10,16)(12,15)(13,21)(14,19)(17,23)(18,22)(20,24)(25,26)(27,28)(29,32)(30,31)(33,34)(35,36)(37,38)(39,40) involution — undirected(1,2)(3,5)(4,6)(7,8)(9,13,14,22)(10,17,12,20)(11,18,19,21)(15,23,16,24)(25,29,30,38)(26,32,31,37)(27,35,34,40)(28,36,33,39)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.