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