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