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