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