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