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