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