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