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