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