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