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)(25,26,29,31)(27,30,34,38)(28,32,35,39)(33,37,36,40)(2,5)(3,8)(9,11)(10,14)(12,19)(13,20)(15,22)(16,23)(17,18)(21,24)(27,33)(28,35)(30,37)(32,39)(34,36)(38,40) involution — undirected(10,15)(13,21)(14,22)(16,17)(18,23)(20,24)(25,27,29,34)(26,30,31,38)(28,36,35,33)(32,40,39,37)(1,3,4,8)(2,6,5,7)(10,16)(11,19)(13,21)(14,22)(15,17)(18,23)(26,31)(30,38)(32,39)(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.