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