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