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