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