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