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