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