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