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