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