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