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