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