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