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