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)(11,17,19,15)(12,16,22,20)(18,24,21,23)(25,26,31,30)(27,32,35,36)(28,33,37,39)(29,34,38,40)(3,7)(5,8)(10,14)(15,17)(16,20)(23,24)(25,27)(26,32)(28,29)(30,36)(31,35)(33,34)(37,38)(39,40) involution — undirected(1,2)(3,5)(4,6)(7,8)(10,14)(15,17)(16,20)(23,24)(27,35)(28,37)(32,36)(33,39) involution — undirected(1,3)(2,5)(4,7)(6,8)(9,10)(11,15)(12,20)(13,14)(16,22)(17,19)(18,24)(21,23)(25,28)(26,33)(27,29)(30,39)(31,37)(32,34)(35,38)(36,40) involution — undirected(1,2)(3,5)(4,6)(7,8)(9,11,13,19)(10,15,14,17)(12,21,22,18)(16,24,20,23)(25,29)(26,34)(27,28)(30,40)(31,38)(32,33)(35,37)(36,39)(9,12,13,22)(10,16,14,20)(11,18,19,21)(15,23,17,24)(25,30,31,26)(27,36,35,32)(28,33,37,39)(29,34,38,40)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.