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