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