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