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