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