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