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