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