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