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