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