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