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