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