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