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