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