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