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)(11,18)(12,21)(13,16)(14,17)(15,20)(19,23)(22,24)(25,26,29,32)(27,34,36,40)(28,33,30,37)(31,38,39,35)(1,3)(2,5)(4,7)(6,8)(9,11)(10,15)(12,19)(13,22)(14,20)(16,23)(17,18)(21,24)(25,26)(27,31)(28,37)(29,32)(30,33)(34,35)(36,39)(38,40) involution — undirected(3,7)(5,8)(25,27,29,36)(26,31,32,39)(28,35,30,38)(33,40,37,34)(9,12,14,13)(10,16,17,21)(11,19,20,22)(15,23,18,24)(26,32)(31,39)(33,37)(34,40)(3,7)(5,8)(9,13,14,12)(10,16,17,21)(11,19,20,22)(15,24,18,23)(25,28,29,30)(26,33,32,37)(27,35,36,38)(31,40,39,34)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.