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