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