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