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