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