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