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