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