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