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