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