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