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)(12,15)(13,22)(14,18)(16,20)(17,23)(21,24)(25,26)(27,33)(28,31)(29,32)(30,35)(34,39)(36,38)(37,40) involution — undirected(1,3,4,7)(2,5,6,8)(9,11,13,12,14,20,23,21)(10,15,17,19,18,24,22,16)(25,27)(26,30)(28,35)(29,34)(31,33)(32,38)(36,37)(39,40)(2,6)(5,8)(11,20)(12,21)(15,24)(16,19)(27,34)(29,37)(30,38)(32,40)(33,39)(35,36) involution — undirected(9,12,13,20,14,21,23,11)(10,16,17,15,18,19,22,24)(26,31)(30,33)(32,40)(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.