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