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