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