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